LOUP POKK EPOGH. 
361 
REVIEW OF THE VERTEBRATE FAUNA OF THE LOUP 
FORK EPOCH. 
-The thirty-two ascertained species of the Santa Fd marls are distributed 
into orders as follows; 
Eeptilia —.... 
Testudiuata .. 
AVES... 
Mammalia ... 
Kodentia.. 
Proboscidea., 
Perissodactyla 
Artiodactyla . 
Carnivora_ 
IncertsB sedis . 
3 
29 
4 
1 
6 
11 
2 
34 
The absence of Fishes and Crocodiles is a noteworthy feature, and is 
true of other deposits of the same age in Colorado and Nebraska. This 
fact, especially the absence of remains of Fishes, suggests that the formation 
is that of a marsh, and not of a lake. This view is confirmed by the nu¬ 
merous vertical streaks, or rods, of a white calcareous mineral, which pene¬ 
trate the soft rock in many places. These resemble the tubes formed by 
the decay of roots of a marsh vegetation, or by the borings of mud-loving 
animals. 
This fauna has now been studied in three widely-separated localities 
in the region west of the Mississippi River. It was first discovered by 
Dr. Hayden, whose collections furnished the basis of Dr. Leidy’s deter¬ 
minations in 1858.* It was next observed by myself in Colorado in 1873,t 
and twenty-one species were determined; and, in the following year, I 
identified the Santa Fd marls of New Mexico, already observed by Dr. 
Hayden, with the same horizon.| There is a near lithological resemblance 
between the strata at these localities, and the fauna presents a common 
character as distinguished from those which preceded and followed it. The 
* See Proc. Acad. Nat. Sci. Phila., 1858, p. 20, and Extinct Mammalia of Dakota 
and Nebraska. 
tBiilletin of tbe U. S. Geolog. Snrv. Terrs., No. 1, Jan., 1874. 
f Ann. Kept. Chief of Engineers, 1874, ii, p. 603. 
