1881.J -*-"*' ICope. 



enters it from the transverse valley. The external portion is the shorter, 

 and exhibits the peculiarity of being connected with external part of the 

 anterior transverse crest. It is as closely connected with this crest, as it 

 is with the internal portion of the posterior crest. The external connec- 

 tion does not exist in the other species of the genus, where the two crests 

 are separated at their outer extremities by a deep valley. The posterior 

 basal cingulum is obsolete, while the anterior is well developed. The 

 enamel of this tooth where not worn, is wrinkled. 



The posterior part of the last inferior molar is characteristic. The 

 posterior transverse crest is short and very oblique, its inner extremity 

 striking the posterior margin near the middle. Here it is elevated into a 

 cusp, which rises above the surrounding parts in a characteristic manner. 

 There is no ledge round its posterior base, but the border expands out- 

 wards at the base of the true crest. The additional inner marginal 

 tubercle is low and compressed as in G. lobatus. A second inferior true 

 molar is normal, with well developed anterior marginal ridge. The in- 

 ferior canine mentioned is of large proportions, exceeding by one -half 

 the dimensions of the inferior canine of 0. lobatus. Its crown is curved 

 outwards, and has a basal alate expansion of its internal ridge. 



_„. „, . , ^anteroposterior 039 



Diameters of last superior molar { , nir1 



1 / transverse 051 



Measurements^ M. 



posterior 039 



erse 051 



_. ,.■,„. c anteroposterior .039 



Diameters of second inferior true molar ? . nno 



I transverse 028 



Length of inferior canine .... .160 



" crown of " . 090 



r vertical 037 



Diameters of base of crown of canine ? transverse Q36 



This species is nearest the C. lobatus in some respects . The short posterior 

 crest ot the last inferior molar with its cusp-like extremity, and the absence 

 of posterior ledge on this tooth will readily distinguish it. 

 Bad lands of the Big-Horn river, Wyoming. 



There are six individuals of this species in the collection which are 

 mostly represented by fine specimens, which represent the entire denti- 

 tion. 



Eight other species of Coryphodon were obtained by the Big-Horn Ex- 

 pedition, and the material enables me to distinguish them better than here- 

 tofore. I present the following differential synopsis of their characters. 

 I. The last inferior molar with three posterior cusps, the internal some- 

 times represented by a ridge ; or the posterior inferior molars with 

 an accessory cusp or tubercle on the inner side between the crests 

 (Ooryphodon, Owen) : 

 An internal tubercle ; last upper molar with the anterior cross crest and an- 

 terior external crest closely connected ; size largest C anax. 



