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。