chap. xi. Mammiferous Remains of. 363 



puma, also, is found from the equator to the Strait of 

 Magellan, and I have seen its footsteps only a little 

 below the limits of perpetual snow in the Cordillera of 

 Chile. 



At the period, so recent in a geological sense, when 

 these extinct mammifers existed, the two Americas 

 must have swarmed with quadrupeds, many of them 

 of gigantic size ; for, besides those more particularly 

 referred to in this chapter, we must include in this 

 same period those wonderfully numerous remains, some 

 few of them specifically, and others generically related 

 to those of the Pampas, discovered by MM. Lund and 

 Clausen in the caves of Brazil. Finally, the facts here 

 given show how cautious we ought to be in judging of 

 the antiquity of a formation from even a great amount 

 of difference between the extinct and living species in 

 any one class of animals ; — we ought even to be cautious 

 in accepting the general proposition, that change in 

 organic forms and lapse of time are at all, necessarily, 

 correlatives. 



SUPPLEMENT. 



On the Thickness of the Pam'pean Formation, near 



Buenos Ayres. 



Kepublished from the ' Proc. of the Geological Soc.' Dec. 3, 1862. 



M. Sourdeaux and J. Coghlan, Esq., C.E., have had the 

 kindness to send me, through E. B. Webb, Esq., C.E., 

 some excellent sections of, and specimens from, two 

 artesian wells lately made at Buenos Ayres. I beg 

 permission to present these specimens to the Geological 



