TheseveralmammifersembeddedinthePampeanformation，whichmostlybelongtoextinctgenera，andsomeeventoextinctfamiliesororders，andwhichdiffernearly，ifnotquite，asmuchasdotheEocenemammifersofEuropefromlivingquadrupedshavingexistedcontemporaneouslywithmollusca，allstillinhabitingtheadjoiningsea，iscertainlyamoststrikingfact。Itis，however，farfrombeinganisolatedone;for，duringthelatetertiarydepositsofBritain，anelephant，rhinoceros，andhippopotamusco-existedwithmanyrecentlandandfresh-watershells;andinNorthAmerica，wehavethebestevidencethatamastodon，elephant，megatherium，megalonyx，mylodon，anextincthorseandox，likewiseco-
existedwithnumerousland，fresh-water，andmarinerecentshells。Manyoriginalobservations，andasummaryonthissubject，aregiveninMr。
Lyell’spaperinthe“GeologicalProceedings“volume4page3andinhis“TravelsinNorthAmerica“volume1page164andvolume2page60。FortheEuropeananalogouscasesseeMr。Lyell’s“PrinciplesofGeology“6theditionvolume1page37。TheenumerationoftheseextinctNorthAmericananimalsnaturallyleadsmetorefertotheformercloserrelationofthemammiferousinhabitantsofthetwoAmericas，whichIhavediscussedinmy“Journal，“andlikewisetothevastextentofcountryoverwhichsomeofthemranged：thusthesamespeciesoftheMegatherium，Megalonyx，Equusasfarasthestateoftheirremainspermitsofidentification，extendedfromtheSouthernUnitedStatesofNorthAmericatoBahiaBlanca，inlatitude39
degreesS。onthecoastofPatagonia。Thefactoftheseanimalshavinginhabitedtropicalandtemperateregions，doesnotappeartomeanygreatdifficulty，seeingthatattheCapeofGoodHopeseveralquadrupeds，suchastheelephantandhippopotamus，rangefromtheequatortolatitude35
degreessouth。ThecaseoftheMastodonAndiumisoneofmoredifficulty，foritisfoundfromlatitude36degreesS。over，asIhavereasontobelieve，nearlythewholeofBrazil，anduptheCordilleratoregionswhich，accordingtoM。d’Orbigny，borderonperpetualsnow，andwhicharealmostdestituteofvegetation：undoubtedlytheclimateoftheCordilleramusthavebeendifferentwhenthemastodoninhabitedit;butweshouldnotforgetthecaseoftheSiberianmammothandrhinoceros，asshowinghowsevereaclimatethelargerpachydermatacanendure;noroverlookthefactoftheguanacorangingatthepresentdayoverthehotlowdesertsofPeru，theloftypinnaclesoftheCordillera，andthedampforest-cladlandofSouthernTierradelFuego;thepuma，also，isfoundfromtheequatortotheStraitofMagellan，andIhaveseenitsfootstepsonlyalittlebelowthelimitsofperpetualsnowintheCordilleraofChile。
Attheperiod，sorecentinageologicalsense，whentheseextinctmammifersexisted，thetwoAmericasmusthaveswarmedwithquadrupeds，manyofthemofgiganticsize;for，besidesthosemoreparticularlyreferredtointhischapter，wemustincludeinthissameperiodthosewonderfullynumerousremains，somefewofthemspecifically，andothersgenericallyrelatedtothoseofthePampas，discoveredbyMM。LundandClauseninthecavesofBrazil。Finally，thefactsheregivenshowhowcautiousweoughttobeinjudgingoftheantiquityofaformationfromevenagreatamountofdifferencebetweentheextinctandlivingspeciesinanyoneclassofanimals;——weoughteventobecautiousinacceptingthegeneralproposition，thatchangeinorganicformsandlapseoftimeareatall，necessarily，correlatives……
LOCALITIESWITHINTHEREGIONOFTHEPAMPASWHEREGREATBONESHAVEBEEN
FOUND。
Thefollowinglist，whichincludeseveryaccountwhichIhavehithertometwithofthediscoveryoffossilmammiferousremainsinthePampas，maybehereafterusefultoageologistinvestigatingthisregion，andittendstoshowtheirextraordinaryabundance。Iheardofandsawmanyfossils，theoriginalpositionofwhichIcouldnotascertain;andIreceivedmanystatementstoovaguetobehereinserted。Beginningtothesouth：——wehavethetwostationsinBahiaBlanca，describedinthischapter，whereatP。
Alta，theMegatherium，Megalonyx，Scelidotherium，Mylodon，Holophractusoranalliedgenus，Toxodon，Macrauchenia，andanEquuswerecollected;andatM。HermosoaCtenomys，Hydrochaerus，someotherrodentsandthebonesofagreatmegatheroidquadruped。Closenorth-eastoftheS。Tapalguen，wehavetheRios’Huesos’i。e。“bones“，whichprobablytakesitsnamefromlargefossilbones。NearVillaNuevo，andatLasAverias，notfarfromtheSalado，threenearlyperfectskeletons，oneoftheMegatherium，oneoftheGlyptodonclavipes，andoneofsomegreatDasypoidquadruped，werefoundbytheagentofSirW。Parishseehiswork“BuenosAyres“etc。page171。I
haveseenthetoothofaMastodonfromtheSalado;alittlenorthwardofthisriver，onthebordersofalakeneartheG。delMonte，Isawmanybones，andonelargepieceofdermalarmour;higheruptheSalado，thereisaplacecalledMonte“Huesos。”OntheMatanzas，abouttwentymilessouthofBuenosAyres，theskeletonvidepage178of“BuenosAyres“etc。bySirW。
ParishofaGlyptodonwasfoundaboutfivefeetbeneaththesurface;herealsoseeCatalogueofRoyalCollegeofSurgeonsremainsofGlyptodonclavipes，G。ornatus，andG。reticulatuswerefound。SignorAngelis，inaletterwhichIhaveseen，referstosomegreatremainsfoundinBuenosAyres，atadepthoftwentyvarasfromthesurface。SevenleaguesnorthofthiscitythesameauthorfoundtheskeletonsofMylodonrobustusandGlyptodonornatus。FromthisneighbourhoodhehaslatelysenttotheBritishMuseumthefollowingfossils：——RemainsofthreeorfourindividualsofMegatherium;ofthreespeciesofGlyptodon;ofthreeindividualsoftheMastodonAndium;ofMacrauchenia;ofasecondspeciesofToxodon，differentfromT。Platensis;andlastly，oftheMachairodus，awonderfullargecarnivorousanimal。M。d’OrbignyhaslatelyreceivedfromtheRecolate“Voyage“Pal。page144，nearBuenosAyres，atoothofToxodonPlatensis。
Proceedingnorthward，alongthewestbankoftheParana，wecometotheRioLuxan，wheretwoskeletonsoftheMegatheriumhavebeenfound;andlately，withineightleaguesofthetownofLuxan，Dr。F。X。Munizhascollected“BritishPacket“BuenosAyresSeptember25，1841，fromanaveragedepthofeighteenfeet，verynumerousremains，ofnolessthan，ashebelieves，ninedistinctspeciesofmammifers。AtAreco，largeboneshavebeenfound，whicharebelieved，bytheinhabitants，tohavebeenchangedfromsmallbones，bythewateroftheriver！AtArrecifes，theGlyptodon，senttotheCollegeofSurgeons，wasfound;andIhaveseentwoteethofaMastodonfromthisquarter。AtS。Nicolas，M。d’OrbignyfoundremainsofaCanis，Ctenomys，andKerodon;andM。Isabelle“Voyage“page332referstoagiganticArmadillofoundthere。AtS。Carlos，Iheardofgreatbones。A
littlebelowthemouthoftheCarcarana，thetwoskeletonsofMastodonwerefound;onthebanksofthisriver，nearS。Miguel，IfoundteethoftheMastodonandToxodon;and“Falkner“page55describestheosseousarmourofsomegreatanimal;Iheardofmanyotherbonesinthisneighbourhood。I
haveseen，Imayadd，inthepossessionofMr。Caldcleugh，thetoothofaMastodonAndium，saidtohavebeenfoundinParaguay;Imayherealsorefertoastatementinthisgentleman’stravelsvolume1page48，ofagreatskeletonhavingbeenfoundintheprovinceofBoliviainBrazil，ontheR。
delasContas。ThefurthestpointwestwardinthePampas，atwhichIhaveHEARDoffossilbones，washighuponthebanksofR。Quinto。
InEntreRios，besidestheremainsoftheMastodon，Toxodon，Equus，andagreatDasypoidquadrupednearSt。FeBajada，IreceivedanaccountofboneshavingbeenfoundalittleS。E。ofP。GordaontheParana，andofanentireskeletonatMatanzas，ontheArroyodelAnimal。
InBandaOriental，besidestheremainsoftheToxodon，Mylodon，andtwoskeletonsofgreatanimalswithosseousarmourdistinctfromthatoftheGlyptodon，foundontheArroyosSarandisandBerquelo，M。Isabelle“Voyage“page322says，manyboneshavebeenfoundneartheR。Negro，andontheR。Arapey，anaffluentoftheParaguay，inlatitude30degrees40
minutessouth。IheardofbonesnearthesourceoftheA。Vivoras。IsawtheremainsofaDasypoidquadrupedfromtheArroyoSeco，closetoM。
Video;andM。d’Orbignyrefers“Voyage“Geolog。page24，toanotherfoundonthePedernal，anaffluentoftheSt。Lucia;andSignorAngelis，inaletter，statesthatathirdskeletonofthisfamilyhasbeenfound，nearCanelones。IsawatoothoftheMastodonfromTalas，anotheraffluentoftheSt。Lucia。ThemosteasternpointatwhichIheardofgreatboneshavingbeenfound，wasatSolisGrande，betweenM。VideoandMaldonado。
CHAPTERV。ONTHEOLDERTERTIARYFORMATIONSOFPATAGONIAANDCHILE。
RioNegro。
S。Josef。
PortDesire，whitepumiceousmudstonewithInfusoria。
PortS。Julian。
SantaCruz，basalticlavaof。
P。Gallegos。
EasternTierradelFuego;leavesofextinctbeech-trees。
SummaryonthePatagoniantertiaryformations。
TertiaryformationsoftheWesternCoast。
ChonosandChiloegroups，volcanicrocksof。
Concepcion。
Navidad。
Coquimbo。
Summary。
Ageofthetertiaryformations。
Linesofelevation。
Silicifiedwood。
ComparativerangesoftheextinctandlivingmolluscaontheWestCoastofS。America。
Climateofthetertiaryperiod。
OnthecausesoftheabsenceofrecentconchiferousdepositsonthecoastofS。America。
Onthecontemporaneousdepositionandpreservationofsedimentaryformations。
RIONEGRO。
IcanaddlittletothedetailsgivenbyM。d’Orbignyonthesandstoneformationofthisdistrict。“Voyage“PartGeolog。pages57-65。Thecliffstothesouthoftheriverareabouttwohundredfeetinheight，andarecomposedofsandstoneofvarioustintsanddegreesofhardness。Onelayer，whichthinnedoutatbothends，consistedofearthymatter，ofapalereddishcolour，withsomegypsum，andverylikeIspeakaftercomparisonofthespecimensbroughthomePampeanmud：abovethiswasalayerofcompactmarlyrockwithdendriticmanganese。Manyblocksofaconglomerateofpumice-pebblesembeddedinhardsandstonewerestrewedatthefootofthecliff，andhadevidentlyfallenfromabove。AfewmilesN。E。ofthetown，Ifound，lowdowninthesandstone，abed，afewinchesinthickness，ofawhite，friable，harsh-feelingsediment，whichadherestothetongue，isofeasyfusibility，andoflittlespecificgravity;examinedunderthemicroscope，itisseentobepumiceoustuff，formedofbrokentransparentcrystals。Inthecliffssouthoftheriver，thereis，also，athinlayerofnearlysimilarnature，butfinergrained，andnotsowhite;itmighteasilyhavebeenmistakenforacalcareoustuff，butitcontainsnolime：thissubstancepreciselyresemblesamostwidelyextendedandthickformationinSouthernPatagonia，hereaftertobedescribed，andwhichisremarkableforbeingpartiallyformedofinfusoria。Thesebeds，conjointlywiththeconglomerateofpumice，areinteresting，asshowingthenatureofthevolcanicactionintheCordilleraduringthisoldtertiaryperiod。
Inabedatthebaseofthesoutherncliffs，M。d’Orbignyfoundtwoextinctfresh-watershells，namely，aUnioandChilina。Thisbedrestedononewithbonesofanextinctrodent，namely，theMegamysPatagoniensis;andthisagainonanotherwithextinctmarineshells。ThespeciesfoundbyM。
d’Orbignyindifferentpartsofthisformationconsistof：——
1。OstreaPatagonica，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe，andwholecoastofPatagonia。
2。OstreaFerrarisi，d’Orbigny，“Voyage，Pal。”
3。OstreaAlvarezii，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe，andS。
Josef。
4。PectenPatagoniensis，d’Orbigny，“Voyage，Pal。”
5。VenusMunsterii，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe。
6。ArcaBonplandiana，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe。
AccordingtoM。d’Orbigny，thesandstoneextendswestwardalongthecoastasfarasPortS。Antonio，anduptheR。Negrofarintotheinterior：
northwardItracedittothesouthernsideoftheRioColorado，whereitformsalowdenudedplain。Thisformation，thoughcontemporaneouswiththatoftherestofPatagonia，isquitedifferentinmineralogicalcomposition，beingconnectedwithitonlybytheonethinwhitelayer：thisdifferencemaybereasonablyattributedtothesedimentbroughtdowninancienttimesbytheRioNegro;bywhichagency，also，wecanunderstandthepresenceofthefresh-watershells，andofthebonesoflandanimals。Judgingfromtheidentityoffouroftheaboveshells，thisformationiscontemporaneousasremarkedbyM。d’OrbignywiththatunderthePampeandepositinEntreRiosandinBandaOriental。Thegravelcappingthesandstoneplain，withitscalcareouscementandnodulesofgypsum，isprobably，fromthereasonsgivenintheFirstChapter，contemporaneouswiththeuppermostbedsofthePampeanformationontheupperplainnorthoftheColorado。
SANJOSEF。
Myexaminationherewasveryshort：thecliffsareaboutahundredfeethigh;thelowerthirdconsistsofyellowish-brown，soft，slightlycalcareous，muddysandstone，partsofwhichwhenstruckemitafetidsmell。
InthisbedthegreatOstraeaPatagonica，oftenmarkedwithdendriticmanganeseandsmallcoral-lines，wereextraordinarilynumerous。Ifoundherethefollowingshells：——
1。OstreaPatagonica，d’Orbigny，“Voyage，Pal。”alsoatSt。FeandwholecoastofPatagonia。
2。OstreaAlvarezii，d’Orbigny，“Voyage，Pal。”alsoatSt。FeandR。
Negro。
3。PectenParanensis，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe，S。Julian，andPortDesire。
4。PectenDarwinianus，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe。
5。Pectenactinodes，G。B。Sowerby。
6。TerebratulaPatagonica，G。B。SowerbyalsoS。Julian。
7。CastsofaTurritella。
ThefourfirstofthesespeciesoccuratSt。FeinEntreRios，andthetwofirstinthesandstoneoftheRioNegro。Abovethisfossiliferousmass，thereisastratumofveryfine-grained，palebrownmudstone，includingnumerouslaminaeofselenite。Allthestrataappearhorizontal，butwhenfollowedbytheeyeforalongdistance，theyareseentohaveasmalleasterlydip。Onthesurfacewehavetheporphyriticgravel，andonitsandwithrecentshells。
NUEVOGULF。
>FromspecimensandnotesgivenmebyLieutenantStokes，itappearsthatthelowerbedconsistsofsoftmuddysandstone，likethatofS。Josef，withmanyimperfectshells，includingthePectenParanensis，d’Orbigny，castsofaTurritellaandScutella。Onthistherearetwostrataofthepalebrownmudstone，alsolikethatofS。Josef，separatedbyadarker-coloured，moreargillaceousvariety，includingtheOstreaPatagonica。ProfessorEhrenberghasexaminedthismudstoneforme：hefindsinitthreealreadyknownmicroscopicorganisms，envelopedinafine-grainedpumiceoustuff，whichI
shallhaveimmediatelytodescribeindetail。Specimensbroughttomefromtheuppermostbed，northoftheRioChupat，consistofthissamesubstance，butofawhitercolour。
Tertiarystrata，suchasheredescribed，appeartoextendalongthewholecoastbetweenRioChupatandPortDesire，exceptwhereinterruptedbytheunderlyingclaystoneporphyry，andbysomemetamorphicrocks;thesehardrocks，Imayadd，arefoundatintervalsoveraspaceofaboutfivedegreesoflatitude，fromPointUniontoapointbetweenPortS。JulianandS。
Cruz，andwillbedescribedintheensuingchapter。ManygiganticspecimensoftheOstraeaPatagonicawerecollectedintheGulfofSt。George。
PORTDESIRE。
Agoodsectionofthelowestfossiliferousmass，aboutfortyfeetinthickness，restingonclaystoneporphyry，isexhibitedafewmilessouthoftheharbour。Theshellssufficientlyperfecttoberecognisedconsistof：——
1。OstreaPatagonica，d’Orbigny，alsoatSt。Fe，andwholecoastofPatagonia。
2。PectenParanensis，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe，S。Josef，S。Julian。
3。Pectencentralis，G。B。SowerbyalsoatS。JulianandS。Cruz。
4。Cucullaeaalta，G。B。SowerbyalsoatS。Cruz。
5。Nuculaornata，G。B。Sowerby。
6。TurritellaPatagonica，G。B。Sowerby。
Thefossiliferousstrata，whennotdenuded，areconformablycoveredbyaconsiderablethicknessofthefine-grainedpumiceousmudstone，dividedintotwomasses：thelowerhalfisveryfine-grained，slightlyunctuous，andsocompactastobreakwithasemi-conchoidalfracture，thoughyieldingtothenail;itincludeslaminaeofselenite：theupperhalfpreciselyresemblestheonelayerattheRioNegro，andwiththeexceptionofbeingwhiter，theupperbedsatSanJosefandNuevoGulf。Inneithermassisthereanytracetothenakedeyeoforganicforms。Takingtheentiredeposit，itisgenerallyquitewhite，oryellowish，orfeeblytintedwithgreen;itiseitheralmostfriableunderthefinger，orashardaschalk;itisofeasyfusibility，oflittlespecificgravity，isnotharshtothetouch，adherestothetongue，andwhenbreathedonexhalesastrongaluminousodour;itsometimescontainsaverylittlecalcareousmatter，andtracesbesidestheincludedlaminaeofgypsum。Underthemicroscope，accordingtoProfessorEhrenberg，itconsistsofminute，triturated，cellular，glassyfragmentsofpumice，withsomebrokencrystals。“Monatsberichtendekonig。Akad。zuBerlin“vomApril1845。Intheminuteglassyfragments，ProfessorEhrenbergrecognisesorganicstructures，whichhavebeenaffectedbyvolcanicheat：inthespecimensfromthisplace，andfromPortS。Julian，hefindssixteenPolygastricaandtwelvePhytolitharia。Oftheseorganisms，sevenarenewforms，theothersbeingpreviouslyknown：allareofmarine，andchieflyofoceanic，origin。Thisdeposittothenakedeyeresemblesthecrustwhichoftenappearsonweatheredsurfacesoffeldspathicrocks;itlikewiseresemblesthosebedsofearthyfeldspathicmatter，sometimesinterstratifiedwithporphyriticrocks，asisthecaseinthisverydistrictwiththeunderlyingpurpleclaystoneporphyry。Fromexaminingspecimensunderacommonmicroscope，andcomparingthemwithotherspecimensundoubtedlyofvolcanicorigin，IhadcometothesameconclusionwithProfessorEhrenberg，namely，thatthisgreatdeposit，initsfirstorigin，isofvolcanicnature。
PORTS。JULIAN。
FIGURE17。SECTIONOFTHESTRATAEXHIBITEDINTHECLIFFSOFTHENINETY
FEETPLAINATPORTS。JULIAN。
Sectionthroughbedsfromtoptobottom：A，B，C，D，E，F。
Onthesouthsideoftheharbour，Figure17givesthenatureofthebedsseeninthecliffsoftheninetyfeetplain。Beginningatthetop：——
1st，theearthymassAA，includingtheremainsoftheMacrauchenia，withrecentshellsonthesurface。
Second，theporphyriticshingleB，whichinitslowerpartisinterstratifiedowing，Ibelieve，toredispositionduringdenudationwiththewhitepumiceousmudstone。
Third，thiswhitemudstone，abouttwentyfeetinthickness，anddividedintotwovarietiesCandD，bothcloselyresemblingthelower，fine-
grained，moreunctuousandcompactkindatPortDesire;and，asatthatplace，includingmuchselenite。
Fourth，afossiliferousmass，dividedintothreemainbeds，ofwhichtheuppermostisthin，andconsistsofferruginoussandstone，withmanyshellsofthegreatoysterandPectenParanensis;themiddlebedEisayellowishearthysandstoneaboundingwithScutellae;andthelowestbedF
isanindurated，greenish，sandyclay，includinglargeconcretionsofcalcareoussandstone，manyshellsofthegreatoyster，andinpartsalmostmadeupoffragmentsofBalanidae。Outofthesethreebeds，Iprocuredthefollowingtwelvespecies，ofwhichthetwofirstwereexceedinglynumerousinindividuals，asweretheTerebratulaeandTurritellaeincertainlayers：——
1。OstreaPatagonica，d’Orbigny，“Voyage，Pal。”alsoatSt。Fe，andwholecoastofPatagonia。
2。PectenParanensis，d’Orbigny，“Voyage，Pal。”St。Fe，S。Josef，PortDesire。
3。Pectencentralis，G。B。SowerbyalsoatPortDesireandS。Cruz。
4。Pectengeminatus，G。B。Sowerby。
5。TerebratulaPatagonica，G。B。SowerbyalsoS。Josef。
6。Struthiolariaornata，G。B。SowerbyalsoS。Cruz。
7。FususPatagonicus，G。B。Sowerby。
8。FususNoachinus，G。B。Sowerby。
9。Scalariarugulosa，G。B。Sowerby。
10。Turritellaambulacrum，G。B。SowerbyalsoS。Cruz。
11。Pyrula，castof，likeP。ventricosaofSowerby，TankCat。
12。Balanusvarians，G。B。Sowerby。
13。Scutella，differingfromthespeciesfromNuevoGulf。
AttheheadoftheinnerharbourofPortS。Julian，thefossiliferousmassisnotdisplayed，andthesea-cliffsfromthewater’sedgetoaheightofbetweenoneandtwohundredfeetareformedofthewhitepumiceousmudstone，whichhereincludesinnumerable，far-extended，sometimeshorizontal，sometimesinclinedorverticallaminaeoftransparentgypsum，oftenaboutaninchinthickness。Furtherinland，withtheexceptionofthesuperficialgravel，thewholethicknessofthetruncatedhills，whichrepresentaformerlycontinuousplain950feetinheight，appearstobeformedofthiswhitemudstone：hereandthere，however，atvariousheights，thinearthylayers，containingthegreatoyster，PectenParanensisandTurritellaambulacrum，areinterstratified;thusshowingthatthewholemassbelongstothesameepoch。Inowherefoundevenafragmentofashellactuallyinthewhitedeposit，andonlyasinglecastofaTurritella。OutoftheeighteenmicroscopicorganismsdiscoveredbyEhrenberginthespecimensfromthisplace，tenarecommontothesamedepositatPortDesire。Imayaddthatspecimensofthiswhitemudstone，withthesameidenticalcharacterswerebroughtmefromtwopoints，——onetwentymilesnorthofS。Julian，whereawidegravel-cappedplain，350feetinheight，isthuscomposed;andtheotherfortymilessouthofS。Julian，where，ontheoldcharts，thecliffsaremarkedas“ChalkHills。”
SANTACRUZ。
Thegravel-cappedcliffsatthemouthoftheriverare355feetinheight：
thelowerpart，toathicknessoffiftyorsixtyfeet，consistsofamoreorlesshardened，darkish，muddy，orargillaceoussandstonelikethelowestbedofPortDesire，containingverymanyshells，somesilicifiedandsomeconvertedintoyellowcalcareousspar。Thegreatoysterisherenumerousinlayers;theTrigonoceliaandTurritellaarealsoverynumerous：
itisremarkablethatthePectenParanensis，socommoninallotherpartsofthecoast，ishereabsent：theshellsconsistof：——
1。OstreaPatagonica，d’Orbigny;“VoyagePal。”alsoatSt。FeandwholecoastofPatagonia。
2。Pectencentralis，G。B。SowerbyalsoP。DesireandS。Julian。
3。VenusmeridionalisofG。B。Sowerby。
4。CrassatellaLyellii，G。B。Sowerby。
5。Cardiumpuelchum，G。B。Sowerby。
6。CarditaPatagonica，G。B。Sowerby。
7。Mactrarugata，G。B。Sowerby。
8。MactraDarwinii，G。B。Sowerby。
9。Cucullaeaalta，G。B。SowerbyalsoP。Desire。
10。Trigonoceliainsolita，G。B。Sowerby。
11。Nucula？glabra，G。B。Sowerby。
12。Crepidulagregaria，G。B。Sowerby。
13。Volutaalta，G。B。Sowerby。
14。Trochuscollaris，G。B。Sowerby。
15。Naticasolida？，G。B。Sowerby16。Struthiolariaornata，G。B。SowerbyalsoP。Desire。
17。Turritellaambulacrum，G。B。SowerbyalsoP。S。Julian。
ImperfectfragmentsofthegeneraByssoarca，Artemis，andFusus。
Theupperpartofthecliffisgenerallydividedintothreegreatstrata，differingslightlyincomposition，butessentiallyresemblingthepumiceousmudstoneoftheplacesfarthernorth;thedeposit，however，hereismorearenaceous，ofgreaterspecificgravity，andnotsowhite：itisinterlacedwithnumerousthinveins，partiallyorquitefilledwithtransversefibresofgypsum;thesefibresweretooshorttoreachacrossthevein，havetheirextremitiescurvedorbent：inthesameveinswiththegypsum，andlikewiseinseparateveinsaswellasinlittlenests，thereismuchpowderysulphateofmagnesiaasascertainedbyMr。Reeksinanuncompressedform：
Ibelievethatthissalthasnotheretoforebeenfoundinveins。Ofthethreebeds，thecentraloneisthemostcompact，andmorelikeordinarysandstone：itincludesnumerousflattenedsphericalconcretions，oftenunitedlikeanecklace，composedofhardcalcareoussandstone，containingafewshells：someoftheseconcretionswerefourfeetindiameter，andinahorizontallineninefeetapart，showingthatthecalcareousmattermusthavebeendrawntothecentresofattraction，fromadistanceoffourfeetandahalfonbothsides。Intheupperandlowerfiner-grainedstrata，therewereotherconcretionsofagreycolour，containingcalcareousmatter，andsofine-grainedandcompact，asalmosttoresembleporcelain-
rock：IhaveseenexactlysimilarconcretionsinavolcanictufaceousbedinChiloe。Althoughinthisupperfine-grainedstrata，organicremainswereveryrare，yetInoticedafewofthegreatoyster;andinoneincludedsoftferruginouslayer，thereweresomespecimensoftheCucullaeaaltafoundatPortDesireinthelowerfossiliferousmassandoftheMactrarugata，whichlattershellhasbeenpartiallyconvertedintogypsum。
FIGURE18。SECTIONOFTHEPLAINSOFPATAGONIA，ONTHEBANKSOFTHES。
CRUZ。
Sectionthroughstratafromtoptobottom：
Surfaceofplainwitherraticboulders;1，146feetabovethesea。
a。Gravelandboulders，212feetthick。
b。Basalticlava，322feetthick。
c，dande。Sedimentarylayers，bedofsmallpebblesandtalusrespectively，total592feetthick。
RiverofS。Cruz;here280feetabovesea。
InascendingthevalleyoftheS。Cruz，theupperstrataofthecoast-
cliffsareprolonged，withnearlythesamecharacters，forfiftymiles：ataboutthispoint，theybegininthemostgradualandscarcelyperceptiblemanner，tobebandedwithwhitelines;andafterascendingtenmilesfarther，wemeetwithdistinctthinlayersofwhitish，greenish，andyellowishfine-grained，fusiblesediments。Ateightymilesfromthecoast，inacliffthuscomposed，therewereafewlayersofferruginoussandstone，andofanargillaceoussandstonewithconcretionsofmarllikethoseinthePampas。Atthisspot，foraspaceofthree-quartersofamilealongthenorthsideoftheriver，andforawidthofhalfamile，therehasbeenagreatslip，whichhasformedhillsbetweensixtyandseventyfeetinheight，andhastiltedthestrataintohighlyinclinedandevenverticalpositions。Thestratagenerallydippedatanangleof45degreestowardstheclifffromwhichtheyhadslided。Ihaveobservedinslips，bothonasmallandlargescale，thatthisinwarddipisverygeneral。Isitduetothehydrostaticpressureofwaterpercolatingwithdifficultythroughthestrataactingwithgreaterforceatthebaseofthemassthanagainsttheupperpart？Atonehundredmilesfromthecoast，thatisatacentralpointbetweentheAtlanticandtheCordillera，wehavethesectioninFigure18。
Theupperhalfofthesedimentarymass，underthebasalticlava，consistsofinnumerablezonesofperfectlywhitebrightgreen，yellowishandbrownish，fine-grained，sometimesincoherent，sedimentarymatter。Thewhite，pumiceous，trachytictuff-likevarietiesareofrathergreaterspecificgravitythanthepumiceousmudstoneonthecoasttothenorth;
someofthelayers，especiallythebrownerones，arecoarser，sothatthebrokencrystalsaredistinguishablewithaweaklens。Thelayersvaryincharacterinshortdistances。WiththeexceptionofafewoftheOstreaPatagonica，whichappearedtohaverolleddownfromthecliffabove，noorganicremainswerefound。Thechiefdifferencebetweentheselayerstakenasawhole，andtheupperbedsbothatthemouthoftheriverandonthecoastnorthward，seemstolieintheoccasionalpresenceofmorecolouringmatter，andinthesupplyhavingbeenintermittent;thesecharacters，aswehaveseen，verygraduallydisappearindescendingthevalley，andthisfactmayperhapsbeaccountedforbythecurrentsofamoreopenseahavingblendedtogetherthesedimentfromadistantandintermittentsource。
Thecolouredlayersintheforegoingsectionrestonamass，apparentlyofgreatthicknessbutmuchhiddenbythetalus，ofsoftsandstone，almostcomposedofminutepebbles，fromone-tenthtotwo-tenthsofaninchindiameter，oftherockswiththeentireexceptionofthebasalticlava
composingthegreatbouldersonthesurfaceoftheplain，andprobablycomposingtheneighbouringCordillera。Fivemileshigherupthevalley，andagainthirtymileshigherupthatistwentymilesfromthenearestrangeoftheCordillera，thelowerplainincludedwithintheupperescarpments，isformed，asseenonthebanksoftheriver，ofanearlysimilarbutfiner-grained，moreearthy，laminatedsandstone，alternatingwithargillaceousbeds，andcontainingnumerousmoderatelysizedpebblesofthesamerocks，andsomeshellsofthegreatOstreaPatagonica。Ifoundatbothplaces，butnotinsitu，quantitiesofconiferousandordinarydicotyledonoussilicifiedwood，whichwasexaminedformebyMr。R。Brown。
Asmostoftheseshellshadbeenrolledbeforebeinghereembedded，theirpresencedoesnotprovethatthesandstonebelongstothegreatPatagoniantertiaryformation，fortheymighthavebeenredepositedinit，whenthevalleyexistedasasea-strait;butasamongstthepebblestherewerenoneofbasalt，althoughthecliffsonbothsidesofthevalleyarecomposedofthisrock，Ibelievethatthesandstonedoesbelongtothisformation。Atthehighestpointtowhichweascended，twentymilesdistantfromthenearestslopeoftheCordillera，Icouldseethehorizontallyzonedwhitebeds，stretchingundertheblackbasalticlava，closeuptothemountains;
sothatthevalleyoftheS。CruzgivesafairideaoftheconstitutionofthewholewidthofPatagonia。
BASALTICLAVAOFTHES。CRUZ。
Thisformationisfirstmetwithsixty-sevenmilesfromthemouthoftheriver;thenceitextendsuninterruptedly，generallybutnotexclusivelyonthenorthernsideofthevalley，closeuptotheCordillera。Thebasaltisgenerallyblackandfine-grained，butsometimesgreyandlaminated;itcontainssomeolivine，andhighupthevalleymuchglassyfeldspar，where，also，itisoftenamygdaloidal;itisneverhighlyvesicular，exceptonthesidesofrentsandontheupperandlower，sphericallylaminatedsurfaces。
Itisoftencolumnar;andinoneplaceIsawmagnificentcolumns，eachfacetwelvefeetinwidth，withtheirintersticesfilledupwithcalcareoustuff。Thestreamsrestconformablyonthewhitesedimentarybeds，butI
nowheresawtheactualjunction;nordidIanywhereseethewhitebedsactuallysuperimposedonthelava;butsomewayupthevalleyatthefootoftheuppermostescarpments，theymustbethussuperimposed。Moreover，atthelowestpointdownthevalley，wherethestreamsthinoutandterminateinirregularprojections，thespacesorintervalsbetweentheseprojectionsarefilleduptothelevelofthenowdenudedandgravel-cappedsurfacesoftheplains，withthewhite-zonedsedimentarybeds;provingthatthismattercontinuedtobedepositedafterthestreamshadflowed。Hencewemayconcludethatthebasaltiscontemporaneouswiththeupperpartsofthegreattertiaryformation。
Thelavawherefirstmetwithis130feetinthickness：itthereconsistsoftwo，three，orperhapsmorestreams，dividedfromeachotherbyvesicularspheroidslikethoseonthesurface。Fromthestreamshaving，asitappears，extendedtodifferentdistances，theterminalpointsareofunequalheights。Generallythesurfaceofthebasaltissmooththeminoneparthighupthevalley，itwassounevenandhummocky，thatuntilI
afterwardssawthestreamsextendingcontinuouslyonbothsidesofthevalleyuptoaheightofaboutthreethousandfeetclosetotheCordillera，Ithoughtthatthecratersoferuptionwereprobablycloseathand。ThishummockysurfaceIbelievetohavebeencausedbythecrossingandheapingupofdifferentstreams。Inoneplace，therewereseveralroundedridgesabouttwentyfeetinheight，someofthemasbroadashigh，andsomebroader，whichcertainlyhadbeenformedwhilstthelavawasfluid，forintransversesectionseachridgewasseentobeconcentricallylaminated，andtobecomposedofimperfectcolumnsradiatingfromcommoncentres，likethespokesofwheels。
Thebasalticmasswherefirstmetwithis，asIhavesaid，130feetinthickness，and，thirty-fivemileshigherupthevalley，itincreasesto322
feet。Inthefirstfourteenandahalfmilesofthisdistance，theuppersurfaceofthelava，judgingfromthreemeasurementstakenabovetheleveloftheriverofwhichtheapparentlyveryuniforminclinationhasbeencalculatedfromitstotalheightatapoint135milesfromthemouth，slopestowardstheAtlanticatanangleofonly0degrees7minutestwentyseconds：thismustbeconsideredonlyasanapproximatemeasurement，butitcannotbefarwrong。Takingthewholethirty-fivemiles，theuppersurfaceslopesatanangleof0degrees10minutes53seconds;butthisresultisofnovalueinshowingtheinclinationofanyonestream，forhalfwaybetweenthetwopointsofmeasurement，thesurfacesuddenlyrisesbetweenonehundredandtwohundredfeet，apparentlycausedbysomeoftheuppermoststreamshavingextendedthusfarandnofarther。Fromthemeasurementmadeatthesetwopoints，thirty-fivemilesapart，themeaninclinationofthesedimentarybeds，overwhichthelavahasflowed，isNOW
afterelevationfromundertheseaonly0degrees7minutes52seconds：
forthesakeofcomparison，itmaybementionedthatthebottomofthepresentseainalinefromthemouthoftheS。CruztotheFalklandIslands，fromadepthofseventeenfathomstoadepthofeighty-fivefathoms，declinesatanangleof0degrees1minute22seconds;betweenthebeachandthedepthofseventeenfathoms，theslopeisgreater。Fromapointabouthalf-wayupthevalley，thebasalticmassrisesmoreabruptlytowardsthefootoftheCordillera，namely，fromaheightof1，204feet，toabout3，000feetabovethesea。
Thisgreatdelugeoflavaisworthy，initsdimensions，ofthegreatcontinenttowhichitbelongs。TheaggregatestreamshaveflowedfromtheCordilleratoadistanceunparalleled，Ibelieve，inanycaseyetknown
ofaboutonehundredgeographicalmiles。Neartheirfurthestextremitytheirtotalthicknessis130feet，whichincreasethirty-fivemilesfartherinland，aswehavejustseen，to322feet。TheleastinclinationgivenbyM。E。deBeaumontoftheuppersurfaceofalava-stream，namely0degrees30minutes，isthatofthegreatsubaerialeruptionin1783fromSkaptarJukulinIceland;andM。E。deBeaumontshowsthatitmusthavefloweddownameaninclinationoflessthan0degrees20minutes。“Memoirespourservir“etc。pages178and217。Butwenowseethatunderthepressureofthesea，successivestreamshaveflowedoverasmoothbottomwithameaninclinationofnotmorethan0degrees7minutes52seconds;andthattheuppersurfaceoftheterminalportionoveraspaceoffourteenandahalfmileshasaninclinationofnotmorethan0degrees7minutes20seconds。
IftheelevationofPatagoniahasbeengreaternearertheCordillerathanneartheAtlanticasisprobable，thentheseanglesarenowalltoolarge。Imustrepeat，thatalthoughtheforegoingmeasurements，whichwereallcarefullytakenwiththebarometer，maynotbeabsolutelycorrect，theycannotbewidelyerroneous。
SouthwardoftheS。Cruz，thecliffsofthe840feetplainextendtoCoyInlet，andowingtothenakedpatchesofthewhitesediment，theyaresaidonthechartstobe“likethecoastofKent。”AtCoyInletthehighplaintrendsinland，leavingflat-toppedoutliers。AtPortGallegoslatitude51
degrees35minutes，andninetymilessouthofS。Cruz，IaminformedbyCaptainSulivan，R。N。thatthereisagravel-cappedplainfromtwotothreehundredfeetinheight，formedofnumerousstrata，somefine-grainedandpale-coloured，liketheupperbedsatthemouthoftheS。Cruz，othersratherdarkandcoarser，soastoresemblegritstonesortuffs;theselatterincluderatherlargefragmentsofapparentlydecomposedvolcanicrocks;thereare，also，includedlayersofgravel。Thisformationishighlyremarkable，fromaboundingwithmammiferousremains，whichhavenotasyetbeenexaminedbyProfessorOwen，butwhichincludesomelarge，butmostlysmall，speciesofPachydermata，Edentata，andRodentia。Fromtheappearanceofthepale-coloured，fine-grainedbeds，IwasinclinedtobelievethattheycorrespondedwiththeupperbedsoftheS。Cruz;butProfessorEhrenberg，whohasexaminedsomeofthespecimens，informsmethattheincludedmicroscopicalorganismsarewhollydifferent，beingfreshandbrackish-waterforms。HencethetwotothreehundredfeetplainatPortGallegosisofunknownage，butprobablyofsubsequentorigintothegreatPatagoniantertiaryformation。
EASTERNTIERRADELFUEGO。
Judgingfromtheheight，thegeneralappearance，andthewhitecolourofthepatchesvisibleonthehillsides，theuppermostplain，bothonthenorthandwesternsideoftheStraitofMagellan，andalongtheeasterncoastofTierradelFuegoasfarsouthasnearPortSt。Polycarp，probablybelongstothegreatPatagoniantertiaryformation，Thesehighertable-
rangesarefringedbylow，irregular，extensiveplains，belongingtotheboulderformationDescribedinthe“GeologicalTransactions“volume6page415。，andcomposedofcoarseunstratifiedmasses，sometimesassociatedasnorthofC。Virgin’swithfine，laminated，muddysandstones。ThecliffsinSebastianBayare200feetinheight，andarecomposedoffinesandstones，oftenincurvilinearlayers，includinghardconcretionsofcalcareoussandstone，andlayersofgravel。Inthesebedstherearefragmentsofwood，legsofcrabs，barnaclesencrustedwithcorallinesstillpartiallyretainingtheircolour，imperfectfragmentsofaPholasdistinctfromanyknownspecies，andofaVenus，approachingverycloselyto，butslightlydifferentinformfrom，theV。lenticularis，aspecieslivingonthecoastofChile。Leavesoftreesarenumerousbetweenthelaminaeofthemuddysandstone;theybelong，asIaminformedbyDr。J。D。Hooker，tothreespeciesofdeciduousbeech，differentfromthetwospecieswhichcomposethegreatproportionoftreesinthisforest-cladland。“BotanyoftheAntarcticVoyage“page212。Fromthesefactsitisdifficulttoconjecture，whetherwehereseethebasalpartofthegreatPatagonianformation，orsomelaterdeposit。
SUMMARYONTHEPATAGONIANTERTIARYFORMATION。
Fouroutofthesevenfossilshells，fromSt。FeinEntreRios，werefoundbyM。d’OrbignyinthesandstoneoftheRioNegro，andbymeatSanJosef。
ThreeoutofthesixfromSanJosefareidenticalwiththosefromPortDesireandS。Julian，whichtwoplaceshavetogetherfifteenspecies，outofwhichthreearecommontoboth。SantaCruzhasseventeenspecies，outofwhichfivearecommontoPortDesireandS。Julian。Consideringthedifferenceinlatitudebetweentheseseveralplaces，andthesmallnumberofspeciesaltogethercollected，namelythirty-six，Iconceivetheaboveproportionalnumberofspeciesincommon，issufficienttoshowthatthelowerfossiliferousmassbelongsnearly，Idonotsayabsolutely，tothesameepoch。Whatthisepochmaybe，comparedwiththeEuropeantertiarystages，M。d’Orbignywillnotpretendtodetermine。Thethirty-sixspeciesincludingthosecollectedbymyselfandbyM。d’Orbignyareallextinct，oratleastunknown;butitshouldbeborneinmind，thatthepresentcoastconsistsofshingle，andthatnoone，Ibelieve，hasdredgedhereforshells;henceitisnotimprobablethatsomeofthespeciesmayhereafterbefoundliving。Somefewofthespeciesarecloselyrelatedwithexistingones;thisisespeciallythecase，accordingtoM。d’OrbignyandMr。
Sowerby，withtheFususPatagonicus;and，accordingtoMr。Sowerby，withthePyrula，theVenusmeridionalis，theCrepidulagregaria，andtheTurritellaambulacrum，andT。Patagonica。Atleastthreeofthegenera，namely，Cucullaea，Crassatella，andasdeterminedbyMr。Sowerby
Struthiolaria，arenotfoundinthisquarteroftheworld;andTrigonoceliaisextinct。Theevidencetakenaltogetherindicatesthatthisgreattertiaryformationisofconsiderableantiquity;butwhentreatingoftheChileanbeds，Ishallhavetoreferagaintothissubject。
Thewhitepumiceousmudstone，withitsabundantgypsum，belongstothesamegeneralepochwiththeunderlyingfossiliferousmass，asmaybeinferredfromtheshellsincludedintheintercalatedlayersatNuevoGulf，S。
Julian，andS。Cruz。Outofthetwenty-sevenmarinemicroscopicstructuresfoundbyProfessorEhrenberginthespecimensfromS。JulianandPortDesire，tenarecommontothesetwoplaces：thethreefoundatNuevoGulfaredistinct。Ihaveminutelydescribedthisdeposit，fromitsremarkablecharactersanditswideextension。FromCoyInlettoPortDesire，adistanceof230miles，itiscertainlycontinuous;andIhavereasontobelievethatitlikewiseextendstotheRioChupat，NuevoGulf，andSanJosef，adistanceof570miles：wehave，also，seenthatasinglelayeroccursattheRioNegro。AtPortS。Julianitisfromeighttoninehundredfeetinthickness;andatS。Cruzitextends，withaslightlyalteredcharacter，uptotheCordillera。Fromitsmicroscopicstructure，andfromitsanalogywithotherformationsinvolcanicdistricts，itmustbeconsideredasoriginallyofvolcanicorigin：itmayhavebeenformedbythelong-continuedattritionofvastquantitiesofpumice，orjudgingfromthemannerinwhichthemassbecomes，inascendingthevalleyofS。Cruz，dividedintovariouslycolouredlayers，fromthelong-continuederuptionofcloudsoffineashes。Ineithercase，wemustconclude，thatthesouthernvolcanicorificesoftheCordillera，nowinadormantstate，wereataboutthisperiodoverawidespace，andforagreatlengthoftime，inaction。
Wehaveevidenceofthisfact，inthelatitudeoftheRioNegro，inthesandstone-conglomeratewithpumice，anddemonstrativeproofofit，atS。
Cruz，inthevastdelugesofbasalticlava：atthissametertiaryperiod，also，thereisdistinctevidenceofvolcanicactioninWesternBandaOriental。
ThePatagoniantertiaryformationextendscontinuously，judgingfromfossilsalone，fromS。CruztoneartheRioColorado，adistanceofabovesixhundredmiles，andreappearsoverawideareainEntreRiosandBandaOriental，makingatotaldistanceof1，100miles;butthisformationundoubtedlyextendsthoughnofossilswerecollectedfarsouthoftheS。
Cruz，and，accordingtoM。d’Orbigny，120milesnorthofSt。Fe。AtS。Cruzwehaveseenthatitextendsacrossthecontinent;beingonthecoastabouteighthundredfeetinthicknessandrathermoreatS。Julian，andrisingwiththecontemporaneouslava-streamstoaheightofaboutthreethousandfeetatthebaseoftheCordillera。Itrests，whereveranyunderlyingformationcanbeseen，onplutonicandmetamorphicrocks。IncludingthenewerPampeandeposit，andthosestratainEasternTierradelFuegoofdoubtfulage，aswellastheboulderformation，wehavealineofmorethantwenty-sevendegreesoflatitude，equaltothatfromtheStraitsofGibraltartothesouthofIceland，continuouslycomposedoftertiaryformations。Throughoutthisgreatspacethelandhasbeenupraised，withoutthestratahavingbeeninasingleinstance，asfarasmymeansofobservationwent，unequallytiltedordislocatedbyafault。
TERTIARYFORMATIONSONTHEWESTCOAST。
CHONOSARCHIPELAGO。
Thenumerousislandsofthisgroup，withtheexceptionofLemus，Ypun，consistofmetamorphicschists;thesetwoislandsareformedofsoftishgreyandbrown，fusible，oftenlaminatedsandstones，containingafewpebbles，fragmentsofblacklignite，andnumerousmammillatedconcretionsofhardcalcareoussandstone。OutoftheseconcretionsatYpunlatitude40
degrees30minutesS。，Iextractedthefourfollowingextinctspeciesofshells：——
1。Turritellasuturalis，G。B。SowerbyalsoNavidad。
2。Sigaretussubglobosus，G。B。SowerbyalsoNavidad。
3。Cytheraea？sulculosa？，G。B。SowerbyalsoChiloeandHuafo？。
4。Voluta，fragmentsof。
Inthenorthernpartsofthisgrouptherearesomecliffsofgravelandoftheboulderformation。InthesouthernpartatP。AndresinTresMontes，thereisavolcanicformation，probablyoftertiaryorigin。Thelavasattainathicknessoffromtwotothreehundredfeet;theyareextremelyvariableincolourandnature，beingcompact，orbrecciated，orcellular，oramygdaloidalwithzeolite，agateandbole，orporphyriticwithglassyalbiticfeldspar。Thereisalsomuchimperfectrubblypitchstone，withtheintersticeschargedwithpowderycarbonateoflimeapparentlyofcontemporaneousorigin。Theselavasareconformablyassociatedwithstrataofbrecciaandofbrowntuffcontaininglignite。Thewholemasshasbeenbrokenupandtiltedatanangleof45degrees，byaseriesofgreatvolcanicdikes，oneofwhichwasthirtyyardsinbreadth。Thisvolcanicformationresemblesone，presentlytobedescribed，inChiloe。
HUAFO。
ThisislandliesbetweentheChonosandChiloegroups：itisabouteighthundredfeethigh，andperhapshasanucleusofmetamorphicrocks。ThestratawhichIexaminedconsistedoffine-grainedmuddysandstones，withfragmentsofligniteandconcretionsofcalcareoussandstone。Icollectedthefollowingextinctshells，ofwhichtheTurritellawasingreatnumbers：——
1。Bullacosmophila，G。B。Sowerby。
2。Pleurotomasubaequalis，G。B。Sowerby。
3。Fususcleryanus，d’Orbigny，“VoyagePal。”alsoatCoquimbo。
4。Tritonleucostomoides，G。B。Sowerby。
5。TurritellaChilensis，G。B。SowerbyalsoMocha。
6。Venus，probablyadistinctspecies，butveryimperfect。
7。Cytheraea？sulculosa？，probablyadistinctspecies，butveryimperfect。
8。Dentaliummajus，G。B。Sowerby。
CHILOE。
Thisfineislandisaboutonehundredmilesinlength。Theentiresouthernpart，andthewholewesterncoast，consistsofmica-schist，whichlikewiseisseenintheravinesoftheinterior。Thecentralmountainsrisetoaheightof3，000feet，andaresaidtobepartlyformedofgraniteandgreenstone：therearetwosmallvolcanicdistricts。Theeasterncoast，andlargepartsofthenorthernextremityoftheislandarecomposedofgravel，theboulderformation，andunderlyinghorizontalstrata。ThelatterarewelldisplayedfortwentymilesnorthandsouthofCastro;theyvaryincharacterfromcommonsandstonetofine-grained，laminatedmudstones：allthespecimenswhichIexaminedareeasilyfusible，andsomeofthebedsmightbecalledvolcanicgrit-stones。TheselatterstrataareperhapsrelatedtoamassofcolumnartrachytewhichoccursbehindCastro。Thesandstoneoccasionallyincludespebbles，andmanyfragmentsandlayersoflignite;ofthelatter，someareapparentlyformedofwoodandothersofleaves：onelayerontheN。W。sideofLemuyisnearlytwofeetinthickness。Thereisalsomuchsilicifiedwood，bothcommondicotyledonousandconiferous：asectionofonespecimeninthedirectionofthemedullaryrayshas，asIaminformedbyMr。R。Brown，thediscsinadoublerowplacedalternately，andnotoppositeasinthetrueAraucaria。Ifoundmarineremainsonlyinonespot，insomeconcretionsofhardcalcareoussandstone：inseveralotherdistrictsIhaveobservedthatorganicremainswereexclusivelyconfinedtosuchconcretions;arewetoaccountforthisfact，bythesuppositionthattheshellslivedonlyatthesepoints，orisitnotmoreprobablethattheirremainswerepreservedonlywhereconcretionswereformed？Theshellshereareinabadstate，theyconsistof：——
1。Tellinides？oblonga，G。B。SowerbyasolenellainM。d’Orbigny’sopinion。
2。Naticastriolata，G。B。Sowerby。
3。Natica？pumila，G。B。Sowerby。
4。Cytheraea？sulculosa，G。B。SowerbyalsoYpunandHuafo？。
Atthenorthernextremityoftheisland，nearS。Carlos，thereisalargevolcanicformation，betweenfiveandsevenhundredfeetinthickness。Thecommonestlavaisblackish-greyorbrown，eithervesicular，oramygdaloidalwithcalcareoussparandbole：mostevenofthedarkestvarietiesfuseintoapale-colouredglass。Thenextcommonestvarietyisarubbly，rarelywellcharacterisedpitchstonefusingintoawhiteglasswhichpassesinthemostirregularmannerintostonygreylavas。Thispitchstone，aswellassomepurpleclaystoneporphyry，certainlyflowedintheformofstreams。
Thesevariouslavasoftenpass，ataconsiderabledepthfromthesurface，inthemostabruptandsingularmannerintowacke。Greatmassesofthesolidrockarebrecciated，anditwasgenerallyimpossibletodiscoverwhethertherecementingprocesshadbeenanigneousoraqueousaction。Inacliffofthehardestfragmentarymass，Ifoundseveraltortuous，verticalveins，varyinginthicknessfromafewtenthsofaninchtooneinchandahalf，ofasubstancewhichIhavenotseendescribed。Itisglossy，andofabrowncolour;itisthinlylaminated，withthelaminaetransparentandelastic;itisalittleharderthancalcareousspar;itisinfusibleundertheblowpipe，sometimesdecrepitates，givesoutwater，curlsup，blackens，andbecomesmagnetic。Boraxeasilydissolvesaconsiderablequantityofit，andgivesaglasstingedwithgreen。Ihavenoideawhatitstruenatureis。Onfirstseeingit，Imistookitforlignite！Thebedsareobscurelyseparatedfromeachother;theyaresometimespartedbyseamsoftuffandlayersofpebbles。Inoneplacetheyrestedon，andinanotherplacewerecappedby，tuffsandgirt-stones，apparentlyofsubmarineorigin。
TheneighbouringpeninsulaofLacuyisalmostwhollyformedoftufaceousdeposits，connectedprobablyintheiroriginwiththevolcanichillsjustdescribed。Thetuffsarepale-coloured，alternatingwithlaminatedmudstonesandsandstonesalleasilyfusible，andpassingsometimesintofine-grainedwhitebedsstrikinglyresemblingthegreatupperinfusorialdepositofPatagonia，andsometimesintobrecciolaswithpiecesofpumiceinthelaststageofdecay;theseagainpassintoordinarycoarsebrecciasandconglomeratesofhardrocks。Withinveryshortdistances，someofthefinertuffsoftenpassedintoeachotherinapeculiarmanner，namely，byirregularpolygonalconcretionsofonevarietyincreasingsomuchandsosuddenlyinsize，thatthesecondvariety，insteadofanylongerformingtheentiremass，wasleftmerelyinthinveinsbetweentheconcretions。Inastraightlineofcliffs，atPointTenuy，IexaminedthefollowingremarkablesectionFigure19：——
FIGURE19。
Onthelefthand，thelowerpartAAconsistsofregular，alternatingstrataofbrowntuffsandgreenishlaminatedmudstone，gentlyinclinedtotheright，andconformablycoveredbyamassBleftofawhite，tufaceousandbrecciolateddeposit。Ontherighthand，thewholecliffBBright
consistsofthesamewhitetufaceousmatter，whichonthissidepresentsscarcelyatraceofstratification，buttotheleftbecomesverygraduallyandratherindistinctlydividedintostrataquiteconformablewiththeunderlyingbedsAA：moreover，afewhundredyardsfurthertotheleft，wherethesurfacehasbeenlessdenuded，thetufaceousstrataBleftareconformablycoveredbyanothersetofstrata，liketheunderlyingonesAA
ofthissection。Inthemiddleofthediagram，thebedsAAareseentobeabruptlycutoff，andtoabutagainstthetufaceousnon-stratifiedmass;
butthelineofjunctionhasbeenaccidentallynotrepresentedsteepenough，forIparticularlynoticedthatbeforethebedshadbeentiltedtotheright，thislinemusthavebeennearlyvertical。Itappearsthatacurrentofwatercutforitselfadeepandsteepsubmarinechannel，andatthesametimeorafterwardsfilleditupwiththetufaceousandbrecciolatedmatter，andspreadthesameoverthesurroundingsubmarinebeds;thematterbecomingstratifiedinthesemoredistantandlesstroubledparts，andbeingmoreoversubsequentlycoveredupbyotherstratalikeAAnotshowninthediagram。ItissingularthatthreeofthebedsofAAareprolongedintheirproperdirection，asrepresented，beyondthelineofjunctionintothewhitetufaceousmatter：theprolongedportionsoftwoofthebedsarerounded;inthethird，theterminalfragmenthasbeenpushedupwards：howthesebedscouldhavebeenleftthusprolonged，Iwillnotpretendtoexplain。Inanothersectionontheoppositesideofapromontory，therewasatthefootofthissamelineofjunction，thatisatthebottomoftheoldsubmarinechannel，apileoffragmentsofthestrataAA，withtheirintersticesfilledupwithwhitetufaceousmatter：thisisexactlywhatmighthavebeenanticipatedundersuchcircumstances。
FIGURE20。GROUNDPLANSHOWINGTHERELATIONBETWEENVEINSAND
CONCRETIONARYZONESINAMASSOFTUFF。
ThevarioustufaceousandotherbedsatthisnorthernendofChiloeprobablybelongtoaboutthesameagewiththosenearCastro，andtheycontain，asthere，manyfragmentsofblackligniteandofsilicifiedandpyritouswood，oftenembeddedclosetogether。Theyalsocontainmanyandsingularconcretions：someareofhardcalcareoussandstone，inwhichitwouldappearthatbrokenvolcaniccrystalsandscalesofmicahavebeenbetterpreservedasinthecaseoftheorganicremainsnearCastrothaninthesurroundingmass。Otherconcretionsinthewhitebrecciolaareofahard，ferruginous，yetfusible，nature;theyareasroundascannon-balls，andvaryfromtwoorthreeinchestotwofeetindiameter;theirinsidesgenerallyconsisteitheroffine，scarcelycoherentvolcanicsandThefrequenttendencyinirontoformhollowconcretionsorshellcontainingincoherentmatterissingular;D’Aubuisson“TraitedeGeogn。”tome1page318remarksonthiscircumstance。，orofanargillaceoustuff;inthislattercase，theexternalcrustwasquitethinandhard。Someofthesesphericalballswereencircledinthelineoftheirequators，byanecklace-likerowofsmallerconcretions。Againtherewereotherconcretions，irregularlyformed，andcomposedofahard，compact，ash-
colouredstone，withanalmostporcelainousfracture，adhesivetothetongue，andwithoutanycalcareousmatter。Thesebedsare，also，interlacedbymanyveins，containinggypsum，ferruginousmatter，calcareousspar，andagate。Itwashereseenwithremarkabledistinctness，howintimatelyconcretionaryactionandtheproductionoffissuresandveinsarerelatedtogether。Figure20isanaccuraterepresentationofahorizontalspaceoftuff，aboutfourfeetlongbytwoandahalfinwidth：thedoublelinesrepresentthefissurespartiallyfilledwithoxideofironandagate：thecurvilinearlinesshowthecourseoftheinnumerable，concentric，concretionaryzonesofdifferentshadesofcolourandofcoarsenessintheparticlesoftuff。Thesymmetryandcomplexityofthearrangementgavethesurfaceanelegantappearance。Itmaybeseenhowobviouslythefissuresdetermineorhavebeendeterminedbytheshape，sometimesofthewholeconcretion，andsometimesonlyofitscentralparts。Thefissuresalsodeterminethecurvaturesofthelongundulatingzonesofconcretionaryaction。Fromthevaryingcompositionoftheveinsandconcretions，theamountofchemicalactionwhichthemasshasundergoneissurprisinglygreat;anditwouldlikewiseappearfromthedifferenceinsizeintheparticlesoftheconcretionaryzones，thatthemass，also，hasbeensubjectedtointernalmechanicalmovements。
InthepeninsulaofLacuy，thestrataoverawidthoffourmileshavebeenupheavedbythreedistinct，andsomeotherindistinct，linesofelevation，rangingwithinapointofnorthandsouth。Oneline，abouttwohundredfeetinheight，isregularlyanticlinal，withthestratadippingawayonbothsides，atanangleof15degrees，fromacentral“valleyofelevation，“
aboutthreehundredyardsinwidth。Asecondnarrowsteepridge，onlysixtyfeethigh，isuniclinal，thestratathroughoutdippingwestward;thoseonbothflanksbeinginclinedatanangleoffromtentofifteendegrees;
whilstthoseontheridgedipinthesamedirectionatanangleofbetweenthirtyandfortydegrees。Thisridge，tracednorthwards，diesaway;andthebedsatitsterminalpoint，insteadofdippingwestward，areinclined12
degreestothenorth。Thiscaseinterestedme，asbeingthefirstinwhichIfoundinSouthAmerica，formationsperhapsoftertiaryorigin，brokenbylinesofelevation。
VALDIVIA：ISLANDOFMOCHA。
TheformationsofChiloeseemtoextendwithnearlythesamecharactertoValdivia，andforsomeleaguesnorthwardofit：theunderlyingrocksaremicaceousschists，andarecoveredupwithsandstoneandothersedimentarybeds，including，asIwasassured，inmanyplaceslayersoflignite。IdidnotlandonMochalatitude38degrees20minutes，butMr。Stokesbroughtmespecimensofthegrey，fine-grained，slightlycalcareoussandstone，preciselylikethatofHuafo，containingligniteandnumerousTurritellae。
Theislandisflattopped，1，240feetinheight，andappearslikeanoutlierofthesedimentarybedsonthemainland。Thefewshellscollectedconsistof：——
1。TurritellaChilensis，G。B。SowerbyalsoatHuafo。
2。Fusus，veryimperfect，somewhatresemblingF。subreflexusofNavidad，butprobablydifferent。
3。Venus，fragmentsof。
CONCEPCION。
SailingnorthwardfromValdivia，thecoast-cliffsareseen，firsttoassumeneartheR。Tolten，andthencefor150milesnorthward，tobecontinuedwiththesamemineralogicalcharacters，immediatelytobedescribedatConcepcion。Iheardinmanyplacesofbedsoflignite，someofitfineandglossy，andlikewiseofsilicifiedwood;neartheToltenthecliffsarelow，buttheysoonriseinheight;andthehorizontalstrataareprolonged，withanearlylevelsurface，untilcomingtoamoreloftytractbetweenpointsRumenaandLavapie。Herethebedshavebeenbrokenupbyatleasteightornineparallellinesofelevation，rangingE。orE。N。E。andW。orW。S。W。Theselinescanbefollowedwiththeeyemanymilesintotheinterior;theyarealluniclinal，thestrataineachdippingtoapointbetweenS。andS。S。E。withaninclinationinthecentrallinesofaboutfortydegrees，andintheouteronesofundertwentydegrees。Thisbandofsymmetricallytroubledcountryisabouteightmilesinwidth。
TheislandofQuiriquina，intheBayofConcepcion，isformedofvarioussoftandoftenferruginoussandstones，withbandsofpebbles，andwiththelowerstratasometimespassingintoaconglomeraterestingontheunderlyingmetamorphicschists。Thesebedsincludesubordinatelayersofgreenishimpureclay，softmicaceousandcalcareoussandstones，andreddishfriableearthymatterwithwhitespeckslikedecomposedcrystalsoffeldspar;theyinclude，also，hardconcretions，fragmentsofshells，lignite，andsilicifiedwood。Intheupperparttheypassintowhite，softsedimentsandbrecciolas，verylikethosedescribedatChiloe;asindeedisthewholeformation。AtLirguenandotherplacesontheeasternsideofthebay，therearegoodsectionsofthelowersandstones，whicharegenerallyferruginous，butwhichvaryincharacter，andevenpassintoanargillaceousnature;theycontainhardconcretions，fragmentsoflignite，silicifiedwood，andpebblesofthesamerockswiththepebblesinthesandstonesofQuiriquina，andtheyalternatewithnumerous，oftenverythinlayersofimperfectcoal，generallyoflittlespecificgravity。Themainbedhereisthreefeetthick;andonlythecoalofthisonebedhasaglossyfracture。Anotherirregular，curvilinearbedofbrown，compactlignite，isremarkableforbeingincludedinamassofcoarsegravel。Theseimperfectcoals，whenplacedinaheap，ignitespontaneously。Thecliffsonthissideofthebay，aswellasontheislandofQuiriquina，arecappedwithredfriableearth，which，asstatedintheSecondChapter，isofrecentformation。Thestratificationinthisneighbourhoodisgenerallyhorizontal;butnearLirguenthebedsdipN。W。atanangleof23degrees;
nearConcepciontheyarealsoinclined：atthenorthernendofQuiriquinatheyhavebeentiltedatanangleof30degrees，andatthesouthernendatanglesvaryingfrom15degreesto40degrees：thesedislocationsmusthavetakenplaceunderthesea。
Acollectionofshells，fromtheislandofQuiriquina，hasbeendescribedbyM。d’Orbigny：theyareallextinct，andfromtheirgenericcharacter，M。
d’Orbignyinferredthattheywereoftertiaryorigin：theyconsistof：——
1。ScalariaChilensis，d’Orbigny，“Voyage，PartPal。”
2。NaticaAraucana，d’Orbigny，“Voyage，PartPal。”
3。Naticaaustralis，d’Orbigny，“Voyage，PartPal。”
4。Fususdifficilis，d’Orbigny，“Voyage，PartPal。”
5。Pyrulalongirostra，d’Orbigny，“Voyage，PartPal。”
6。PleurotomaAraucana，d’Orbigny，“Voyage，PartPal。”
7。Cardiumauca，d’Orbigny，“Voyage，PartPal。”
8。Cardiumacuticostatum，d’Orbigny，“Voyage，PartPal。”
9。Venusauca，d’Orbigny，“Voyage，PartPal。”
10。Mactracecileana，d’Orbigny，“Voyage，PartPal。”
11。MactraAraucana，d’Orbigny，“Voyage，PartPal。”
12。ArcaAraucana，d’Orbigny，“Voyage，PartPal。”
13。NuculaLargillierti，d’Orbigny，“Voyage，PartPal。”
14。TrigoniaHanetiana，d’Orbigny，“Voyage，PartPal。”
Duringasecondvisitofthe“Beagle“toConcepcion，Mr。KentcollectedformesomesilicifiedwoodandshellsoutoftheconcretionsinthesandstonefromTome，situatedashortdistancenorthofLirguen。Theyconsistof：——
1。Naticaaustralis，d’Orbigny，“Voyage，PartPal。”
2。MactraAraucana，d’Orbigny，“Voyage，PartPal。”
3。TrigoniaHanetiana，d’Orbigny，“Voyage，PartPal。”
4。Pecten，fragmentsof，probablytwospecies，buttooimperfectfordescription。
5。Baculitesvagina，E。Forbes。
6。Nautilusd’Orbignyanus，E。Forbes。
Besidestheseshells，CaptainBelcherfoundhereanAmmonite，nearlythreefeetindiameter，andsoheavythathecouldnotbringitaway;fragmentsaredepositedatHaslarHospital：healsofoundthesilicifiedvertebraeofsomeverylargeanimal。“ZoologyofCaptainBeechey’sVoyage“page163。