58 F. B. Loomis — Rkinocerotidce of the Lower Miocene. 



incomplete. The crochet and crista are united, thus isolating 

 the median fossette, and on the outer face of the crochet wall 

 are tiny ridges which gave a crenulated appearance to the 

 enamel wall when worn. On the molars the anterior cingulum 

 is weak, the internal one wanting, and that on the posterior 

 border is raised. While the crochet is large, it does not unite 



Fig. 8. Dicer atherium schiffi ; left upper premolar and molar series of the 

 type ; one-half nat. size. 



with the moderate crista. The species has affinities with D. 

 cooki, but is smaller and of lighter build ; has a wide flat skull 

 in contrast to the high and narrower one of D. cooJci. It 

 has also the crista better developed. 



In the experience of the Amherst part this was the common- 

 est species, there being in the collection three incomplete 

 skulls and several jaws. 



Dlceratherium cooki Peterson. 

 Science, vol. xxiv, p. 281, 1906. 



The type of the species is a skull in the Carnegie Museum, 

 from the Lower Harrison beds of the Agate Spring Quarry, 

 Sioux Co., Nebraska. 



The heavily built skull is relatively short and high, with a 

 high occipital crest and a moderate sagittal crest formed by the 

 confluence of the two ridges from over the orbits. The orbit 

 is small, and narrow zygomatic arch of moderate weight. The 

 nasal bones do not project in front of the horn cores, but end 

 abruptly, giving the skull a very characteristic appearance. On 

 the premolars, the cingulum is greatly reduced ; while the 

 strong crochet unites with the feeble crista, thus isolating the 

 median fossette. In like manner on the molars, the cingulum 

 is reduced to traces on the front, inner side, and rear of the 

 teeth. The crochet is very large and the crista weak, but the 

 two do not unite. 



As noted above, this species resembles in dentition D. schiffi, 

 but has a shorter and higher skull, with a sagittal ridge, where 

 the latter has a broad flat area. The crochet is larger and the 

 crista weaker than in D. schiffi. 



