368 OC. A. White—Fossil Faunas and Floras. 
them if they had not been found to contain the vertebrate 
remains in question.* According to Professor Cope this 
Puerco fauna is, as a whole, quite unlike any vertebrate fauna 
that is now known to have either preceded or followed it upon 
this continent ; although certain of its types are related to some 
that are found in the Laramie and Wasatch Groups respectively. 
Still, in consequence of the presence of certain types which he 
regards as Mesozoic, Professor Cope thinks the fauna possesses 
more of a Cretaceous, than of a Tertiary character. ‘lhe 
lowest strata in which the remains of this fauna have yet been 
found closely coincide in position with the top of the Laramie 
Group ; and they disappear suddenly upon a certain higher 
horizon which seems to come within the basal portion of the 
Wasatch Group. Moreover, the known area within which 
this Puerco fauna has been found is only a small part of that 
within which the Laramie and Wasatch groups occur. That 
is, the Puerco fauna has not been recognized at the majority of 
the localities where the Wasatch has been found overlying the 
Laramie. In some of the latter cases the two formations have 
been found to be closely connected, not only by: strict con- 
formity of the strata, but also by an intermingling of their 
molluscan faunas; and in none of them has any indication of 
a missing formation been observed. 
The next vertebrate fauna to be considered is that of the 
Wasatch Group, which is a remarkable one for its abundant 
variety and diversity of forms. All persons who have studied 
this fauna agree in regarding it as of Hocene age, including as 
it does Coryphodont and other distinctly Hocene types. With 
this reference the plant and vertebrate forms agree, except that 
some of the former have been regarded as of later Tertiary 
types. The Coryphodont and other Kocene vertebrate remains 
referred to have been found in the lowermost of the Wasatch 
strata as well as at higher horizons in the group, and, as before 
said, some of the Laramie dinosaurs have been found in the 
uppermost strata of the latter group. 
Above the Wasatch Group proper, the Coryphodonts soon 
disappear, and other changes in the Hocene vertebrate fauna 
gradually take place up to the close ‘of the Bridger Group. 
Above the Bridger Group the vertical continuity of the intra- 
continental Tertiary deposits of that western region is broken. 
That is, the later fresh-water Tertiary deposits were formed in 
isolated basins, and they therefore do not constitute part of a 
continuous series, with that of the preceding deposits. Conse- 
quently the geological age of those later deposits must be 
determined by means of their fossil contents alone, without the 
* For a concise account of the Puerco by Professor Cope, see Am. Naturalist, 
xix, p. 985. See also same volume, pp. 385 and 493. 
