GEOLOGICAL SURVEY OF THE TERRITORIES. 365 



Omomys Garteri. — The species, named in honor of its discoverer, was 

 about half as large again as our common mole, (Scalops aquaticus.) 



EDENTATA. 



Among the great multitude of vertebrate fossils brought to our notice 

 from the western part of the continent, we have detected almost no 

 traces of remains of the giant sloths, which existed so extensively dur- 

 ing the quaternary period in both North and South America. .Remains 

 of Mylodon Harlani have been found on the Willamette Eiver, Oregon, 

 and recently we have seen the fragment of a claw phalanx, apparently 

 of a large, sloth-like animal, from Castle Creek, Idaho. 



CETACEA. 



Eemains of cetaceans, thus far, have been but sparingly found in the 

 tertiary and quaternary formations of the West. Vertebrae from the 

 later deposits have been indicated from Oregon. 



DELPHINUS. 



Remains of porpoises have been discovered in the upper miocene 

 formation of Half-Moon Bay, California. 



Delphinus occiduus. — A species, founded upon a jaw fragment from 

 the locality just named, submitted to the examination of the writer by 

 Professor J. D. Whitney. It was about the size of our common porpoise* 



BIRDS. 



The remains of birds are among the rarest of vertebrate fossils in 

 most of the explored rocks of the world. From the peculiarities of these 

 animals, enabling them to escape many of the catastrophes or accidents 

 to which more terrestrial and aquatic animals would be liable, and from 

 the generally lighter construction of their bodies, they are less likely to be 

 placed in positions where their remains would be preserved and become 

 fossils. Among the large collections of fossils made in the mauvaises 

 terres of White River, Dakota, amounting to several tons in weight, 

 which have been submitted to the writer's examination, he discovered 

 no trace of birds. In all other collections from the West there was 

 likewise no trace detected, except a single bone fragment discovered 

 by Dr. Hayden in the pliocene sands of the Niobrara River, Nebraska. 

 This specimen has been recently described by Professor O. C. Marsh, 

 who views it as pertaining to an extinct species, to which he has given 

 the name of Grus Haydeni. 



BEPTILES. 



The remains of reptiles occur in the greatest abundance in the second- 

 ary formations of the West. Those best known have been derived from 

 the cretaceous deposits of Kansas, Dakota, and of the head-waters of 

 the Missouri Eiver. Remains of the same order, though less abundant, 

 are nevertheless quite numerous in the tertiary deposits of the country, 

 especially those of turtles. 



CHELONIA. 



The chelonians or turtles appear to have been exceedingly abundant 

 in the West during the tertiary period. They, however, appear not to 



