258 Bulletin American Museum of Natural History. [Vol. XIII, 



Cranial characters. — Nasals short and broad, triangular when seen from 

 above ; median horn precociously (Middle Miocene) developed upon both nasals 

 and frontals ; occiput both broad and high (very distinct from Aceratherine, 

 Diceratherine, or Brachypodine types). 



a. Lower Level, Satisan. 



R. sansaniensis. — Paris : The type skull (No. 2395, Coll. 

 Lartet, Sansan) is that of a male, a small animal ; it is very much 

 crushed antero-posteriorly, disguising its real dolichocephalic char- 

 acter, which is strongly marked in the uncrushed lower jaw ; the 

 first lower premolar has a broad double or grooved fang, while in 

 R. simorrensis this tooth is small and single-fanged ; the premolars 

 are greatly worn so that the median valley has almost disappeared 



P^ p3 



Fig. 14. Lower grinding series. A, R. sansaniensis. Paris. B, R. simorrensis. Paris. 



and the crests are quite confluent : although a male (because of 

 its well developed horns) the inferior canines are smaller than in 

 the R. simorrensis jaw ; the simple character of the molar crests 

 in this specimen is deceptive, and is due to extreme wear, the 

 crochet (a superficial fold) having been worn off, the protocone 

 and antecrochet are indistinctly marked (quite unlike the Ace- 

 ratheriinge and Brachypodinte of this geological period) ; the in- 

 ner face of the molars is without cingulum (unlike Aceratheriinae 

 and Brachypodinse) ; there are indications that young teeth would 

 show both crista and crochet ; the nasals and occiput have a very 

 characteristic shape, somewhat similar to that of Gaudry's R. 

 schleiermacheri of Pikermi ; the nasals are especially distinctive, 

 being broad and rugose behind, where they carry the horn, 

 but converge to a smooth point anteriorly ; (See Paris, Nos. 

 2395, 551); metatarsals (erroneously catalogued A. tetradactylum), 

 of moderate length, probably belong to this species. 



