C 
1871.] 99 [Cope. 
GENERAL OBSERVATIONS. 
Several authors have noticed the great difference in character between 
the postpliocene fauna of North America, and those which preceded it, 
in Tertiary time. It is well known, that while the Miocene Mammalia are 
more or less similar to those of Miocene Europe and Asia, and the Plio- 
cene vertebrata have a corresponding resemblance to those of the same 
period of Europe and Asia, and the present one of Africa, the postplio- 
cene resembles, in many particulars, that of South America or the Neo- 
tropical region. 
In examining the list of postpliocene mammailia, known up to 1867,* 
T found, that of 30 species, eleven were represented by members of the 
same genus or family, in the Neotropical region. In an enumeration of 
the species from the caves in 1869, which included 27 species of 23 gene- 
ra, six genera were shown to be of neotropical type. In an unpublished 
list of vertebrata, which the writer exhumed in a bone breccia, from a cave 
in East Tennessee, there are twenty species included. Prominent among 
these, are Megalonyx, Dicotyles, Tapirus, Cervus, and Sciurus, the first 
three neotropical. The species from the Port Kennedy bone cave may 
be arranged as follows: 
Species. 
Neotropical forms. 06s... 240 28 ce ee via 
Peculiar Nearctic (North America).........-6..---. eee cess eee 3 
Genera common to north of both Hemispheres............... oi wen 
WHCONDAIN Gye esc cs ee ee nee ee a oe es os 9 
TROL es Werks oact bees PU eto ia te a ee enn 34 
The theory of evolution requires that change of fauna in any very 
brief period of geologic time, should be accomplished by migration. Ac- 
cordingly, authors have suspected that Asia and North America, and 
perhaps Europe, were connected by land during the miocene period. 
Thus Leidy, (Mammalia of Dakota and Nebraska, 1869, p. 360), suspects. 
that North America was peopled from the west, from a continent now 
submerged beneath the Pacific Ocean. Prof. Huxley (Anniv. Address, 
Lond. Geolog. Society, 1870), makes a similar proposition, but adds that 
there is no evidence as to whether the connection was with Europe or 
Asia. In describing fossil Cobitide, a family of fresh water fishes, from 
Idaho, in 1871, (Proceed. Am. Philo. Soc., p. 55,) I have adduced evidence 
that the connection was with Asia. These Coditidw, as is well known, 
have no existing representatives in America, and are one of the Asiatic 
types, characteristic of our Pliocene period. As fresh water fishes, their 
migration is restricted to fresh water communication. Now, as the Rocky 
Mountain ranges were in large part elevated prior to Pliocene time, and 
the water courses had their present directions, it is obvious that the mi- 
gration of fresh water fishes occupying waters on the west side of those 
ranges, must have been to or from the west, and not the east. That these 
*Pyoc. Acad, Nat. Sci. Phila. 1867, 156. + Proceed. Am. Phil. Soc. 1869, 178. 
