)8 Bulletin American Museum of Natural History. [Vol. XIII, 



Additional Characters. — Paris : Cuvier's type : Fourth superior premolar 

 with protoloph and metaloph confluent in old age, small antecrochet; molars 

 with antecrochet, crochet, metaconule fold, postfossette, and median internal 

 cingule. Duvernoy'' s type (R. pleuroceros) : molars agreeing precisely in size 

 with above ; skull and jaws of dolichocephalic type, paired horn-cores on nasals, 

 occiput narrow elevated ; zygomatic arch convexity as in Ccenopus tridactytiis 

 Osborn. In the Paris jaw (Gannat) the first lower premolar is wanting, in 

 Munich and Lyons specimens it is vestigial, indicating that, as in the American 

 Diceratheriinge, this tooth was variable ; m i-m 3 = 100. Tibia (Gannat) ;= 260. 

 Munich and Stuttgart (Eselsberg, Ulm, specimens) : first lower premolar very 



small ; pm 2-4 molariform with 

 elevated posterior crests ; lower 

 canines sharp, subtriangular 

 with flattened outer surface, 

 flat upper face partly destitute 

 of enamel, slightly convex lower 

 face and sharp inner edge ; ca- 

 nines large in males, small in 

 females (this tooth is very sim- 

 ilar to the canines of the 

 American species C. tridactyliis 

 Osborn) ; unworn premolars 

 (catalogued A. croizeti, Mu- 

 nich) as in Cuvier's type with- 

 out antecrochet, but with crista 

 and pectinate crochet (see Nos. 4757, 9861, Stuttgart, Eggingen) ; unzvorn 

 molars exhibit crista, crochet, and antecrochet, while worn molars lose crista 

 and show greater prominence of antecrochet and crochet, and postfossette 

 (especially in p 4-m 2), also an internal cingule or cusp in the median valley as 

 in American Diceratheres. This animal is exactly the size of Canoptts mite of 

 the American Lower Oligocene. Lyons: A small jaw (catalogued A. croizeti) 

 with vestigial pm i. 



Fig. 5a. Diceratheritim minutuin. A, Type 

 premolar and molars. X 5. Paris. B, Part of left 

 superior grinding series. Ulm, Munich. 



Affinities. — By this comparison there is little question that all 

 these teeth belong to the Upper Oligocene Diceratherium and, so 

 far as we know, to the single species D. minutum Cuvier, which 

 presents many features of close resemblance to the American 

 Diceratheres. In Paris the skull of the Upper Oligocene D. 

 {Pleuroceros^ minutu7n is now placed in the case side by side with 

 that of the Middle Oligocene Ccenopus Occident alls from South 

 Dakota ; it exhibits a remarkable similarity in the form of the 

 occiput, the zygoma, and the paroccipital region. 



