350 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



ON THE VERTEBRATE FOSSILS OF THE WAHSATCH STRATA. 



By Edward D. Cope, A. M. 



Dr. Hayclen's researches in Utah and Wyoming have demonstrated 

 the existence of an extensive series of fresh-water deposits, containing 

 numerous remains of animals and plants. Those of Western Wyoming, 

 or the Bridger series, are regarded as Upper Eocene or Lower Miocene. 

 They thin out to the westward, and a new series of strata takes their 

 place, dipping to 'the eastward. The Bridger beds are not strictly 

 conformable to them, while they rest uucomformably on a bottom-rock of 

 Cretaceous age. These are the Wahsatch beds of Hayden. He informs 

 us that they consist largely of variegated ferruginous rocks, very defi- 

 cient in fossils. During his recent exploration, however, he procured a 

 number of bones of mammalia from Utah, and placed them in my hands 

 for determination. The following description expresses their charac- 

 ters, from which it is obvious that the forms they represent were of 

 much interest in a systematic^oint of view. 



Order Perissodaciyla. 



BATHMODON, Cope. 



Proc. Amer. Pliilos. Soc, 1872, February 16. 



The present form embraces some of the largest Perissodactyles, or 

 odd-toed JJngulata, of our Tertiary strata. It is represented by remains 

 of two species, which include portions of the cranium, with teeth and 

 fragments of jaws, vertebrae, fragments of scapular and pelvic arches, 

 and bones of the limbs. The distal end of the tibia is wanting, but that 

 of the fibula indicates an odd-toed animal, and the third trochanter on 

 the exterior ridge of the femur confirms the reference. 



There are probably four superior molars, though three only are pre- 

 served. Two premolars only remain of the superior series, but the frag- 

 ment of ramus mandihuU referred to the same species exhibits four 

 premolars ; from a consideration of the sizes of the superior premolars 

 it is probable that there were four of these also. There are three strong 

 incisors in each premaxillary. No canine tooth is preserved, but the 

 posterior suture of the premaxillary bone is so wide as to point to an 

 equally stout anterior part of the maxillary fitted to support such a 

 tooth. The dental series increases regularly in size, from before back- 

 ward, the last being a little larger than the penultimate. The crowns 

 of the molars exhibit on the outer margin a single acutely angled cres- 

 cent directed inward, with a conic lobe alongside of and anterior to its 

 base, representing a second external crescent. The crescent lobe proper 

 is large and very obliquely directed, so that its external face is almost 

 horizontal. The apex of its companion cone is continuous with its pos- 

 terior margin, so as to be undistinguishable from it in some cases. The 

 inner crescents are represented by a wide angular ridge, which is at a 

 lower level than the exterior, and is little or not developed on the pos- 

 terior side of the crown. Its inner ijlane face is horizontal, or even as- 

 cending in one species. In the premolar teeth of B. radians the external 

 crescent lobe is single and symmetrical. As the crown contracts 

 inwardly a second inner crescent lobe has a trihedral form, while in one 

 more anterior the inner is much reduced. The inferior premolars are 



