236 BULLETIN UNITED STATES GifOLOGICAL SUEVEY. [YoLY. 



APHELOPS Cope. 



Paleontological Bulletin, No. 14, p. 1, July 25, 1873. — ^Proceedingfi Amer. Philosophical 

 Society, 1873, (1874), p. 520.— Hayden's Ann. Eeport U. S. Geol. Survey Terrs., 

 1873, (1874), p. 519.— Eeport U. S. Geol. Geogr. Surv. W. of 100th Mer., G. M. 

 "Wheeler, vol. iv, pt. ii, p. 315. 



Dental formula; l.l^- C. f; Pm. t^; M. f. Digits 3—3. i^asal 

 bones witli persistent suture, weak, not supporting a dermal horn. 



This genus occui^ies a position intermediate between AceratJierium 

 Kaup and Ehinocerus Linn. It agrees^witli the former in the presence 

 of incisor and canine teeth, and in the absence of indication of a nasal 

 horn, but differs from it in lacking the fifth digit of the anterior foot. 

 In the last respect it is identical with the genus EJiinocerus, differing 

 from it in characters already mentioned, in which it agrees with Ace- 

 ratherium. From Atelodus Pom. it differs still more widely, as that 

 genus wants incisor and canine teeth. 



The evidence on which this genus rests is furnished by two species, 

 the Aphelops onegalodiis, and a second form, whose bones I have provi- 

 sionally associated with the crania of A. fossiger. In both of these ani- 

 mals, the number of anterior digits is known to be only three, and in 

 the former the inferior canines and alveoh for incisors can be seen in 

 the specimens. In two other species provisionally referred to the same 

 genus, the A. crassus and A. malacorhinus, the digits and incisor teeth 

 are unkown, but the last named species was certainly hornless, and it is 

 supposed that the first named was so also. Of the many mandibu- 

 lar symphyses from the Loup Fork formation which I have seen, none 

 lack the canines and incisor teeth, so that it is probable that this 

 character belonged to the two species above mentioned. A fifth species, 

 the A. meridiamis Leidy, I have provisionally referred here on account 

 of the similar character of the mandibular dentition; but its nasal bones 

 and feet are unknown. Still another species, the A. jemezanus Cope, 

 has been referred here, but on no other ground than that it is found in 

 the same formation as the others. 



Specific cJiaracters. — The species above named all present well-marked 

 cranial or dental characters, or both. But it is imi^ortant to take into 

 consideration the general structure of the skeleton. I am in jjosition to 

 do this with three of the species named, the A. megalodtis,the A.fossiger 

 (of this paper), and the A. mcdacorhimis, and find distinctive characters 

 present in nearly all their bones which I have olDserved. The A. mala- 

 corhinns is a comparatively long-limbed animal, and its apparent eleva- 

 tion was increased by the shortness of the body, and especially of the 

 neck. There was probably a great development of the upper lip, or 

 snout, and tlie face was concave in profile. The A. megalodus was some- 

 what intermediate in proportions between this species and the A. cras- 

 sus. Its limbs were shorter than in the A. onalacorliinus, and the neck 

 was longer. The feet were more slender. The A. fossiger had still 

 shorter legs, and the length of the neck was about as in A. malacorliinus. 



