THE LOUP FORK BEDS. 
25 
Placita Creek and its tributary arroyos, vvhicli furnish interesting sections, 
From these it appears that the greater part of the plateau consists of 
the yellow, muddy shales and sandstones of Cretaceous No. 3. They 
form the bottoms, and sometimes the walls of the arroyos, and rise in low 
monoclinal hills at various points on the plateau. The beds dip N.W. 20° 
to 40°. In the intervals between the hills, there is a deposit of indurated 
clay of 40 feet in thickness, of Postpliocene age. I obtained teeth and 
other bones of ElepJias primigenius subspecies columhi from this bed, and 
found bones of Elephants in place in the banks of the arroyo. Shells of 
Planorhis, PJiysa, &c., indicate the lacustrine character of the deposit, which 
I have called the Placita marl.* 
The descriptions and determinations of the species of the Santa and 
Placita marls were published in the following essays: 
1874.—Proceedings of the Philadelphia Academy, p. 147, Notes on the Santa F^ marls, 
and some of the contained fossils, by E. D. Cope. 
1874, November 28.—Report upon Vertebrate fossils discovered in New Mexico, with 
descriptions of new species, by E. D. Cope, p. 15. Annual Report Chief of Engi¬ 
neers, pt. 2, p. 603. 
1874.—Annual Report of Chief of Engineers, ii, p. 603. 
1874. —Proceedings Academy Philadelphia, 221, On a new Mastodon and Rodent. 
1875. —Proceedings Academy Philadelphia, p. 255, On fossil Lemurs and Dogs. 
1875.—Proceedings Academy Philadelphia, 257, On the Antelope-deer of the Santa Fd 
marls, and the age of the formation. 
1875.—Proceedings Academy Philadelphia, p. 258, On some new fossil Ungulata. 
1875.—Proceedings Academy Philadelphia, p. 261, The phylogeny of the Camels. 
1875.—Proceedings Academy Philadelphia, p. 271, On an extinct Vulturine Bird. 
1875. —Annual Report of Chief of Engineers, ii, p. 988, On the Vertebrate paleontology 
of the Santa Fd marls; 1. c. 986, On Mastodon from Taos; 1. c. 997, On Eleylias 
from Placita. 
1876. —Proceedings Philadelphia Academy, July, on Ganis wheelerianus and the evolu¬ 
tion of the camels. 
•Annual Report of Chief of Engineers, 1875, p. 997. 
