27 



as an external crescent. The canine of the inferior series stands in the 

 middle of a considerable diastema, which is preceded by three incisors. 



Char, specif. — The second superior premolar is quite short, and its in- 

 ner lobe small. The last premolar has a strong cinguluoi on the ante- 

 rior and especially on the posterior faces of the last premolar. The 

 superior molars have no rib nor column opposite the interval between the 

 crescents ; the last molar exhibits four ribs on the outer side. The sec- 

 ond (third) inferior premolar is compressed and elevated and mucli 

 shorter than the third, which is threelobed. The j)osterior crescents of 

 the last inferior molar are opposite and not separated posteriorly by a 

 fissure. 



This very abundant species of musk is a little smaller than the 

 Leptomeryx evansii. 



Hypertragulus tricostatus, sp. UOV. 



Eepresented by the superior molars of one individual, and, perhaps, 

 by numerous mandibles, which I cannot certainly associate with them. 

 The last premolar has, as in the preceding species, a strong posterior 

 cingulum, but there are only three ribs on the outer side of the third 

 molar, the characteristic heel being absent. The latter also lacks the 

 cingulum which passes round inner side of the bases of the crowns in 

 C. calcaratus, its representative being the basal tubercle between the 

 inner lobes of that and the other molars. 



Leptomeryx evansii Leidy, Anc. Fauna Dak., Nebr., p. 165 ; Tri- 



merodus cedrensis Cope, Pal. Bullet., ISTo. 16, p. 8. 



The form of premolars characteristic of Trimerodus, as cited, pertains 

 also to this genus. The species represents the smaller forms, but I find 

 a considerable range in size in the numerous specimens obtained, and 

 do not, at present, regard them as belonging to more than one species. 

 IscHYROMYS TYPUS Leidy, I. chrysodon Cope, Synopsis Vert. Col., 



1873, p. 2 ; Colotaxis cristatus Cope, Pal. Bull., 15, p. 1. 



This species varies considerably in the form of the premolar teeth, 

 and I believe the above names refer to varieties, not species. 



Elotherium ramosum Cope, sp. nov. 



Established on the greater part of a mandible, with teeth from a 

 cranium which, when complete, must have measured nearly two feet 

 and a half in length, indicating an animal not smaller than the largest 

 living rhinoceroses. The species is remarkable for the great size of the 

 tubercles on the under side of the mandibular ramus, especially the 

 anterior pair. The symphysis is narrow, and the tuberosities form two 

 branches, whose bases occupy the entire lower part of its anterior face. 

 They are several inches long, and directed outward and downward. 

 The posterior edge is acute, and the extremitj^ very rugose, as though 

 for the attachment of a horny cap. The outer face is flat, the inner con- 

 vex. The second tuberosity is below the first true molar, is flat and 

 turned outward, with apex obtuse in profile. The molar teeth number 

 seven -, the first and second of the four premolars are separated by a 

 diastema, and have but a single root. The tubercles of the molars 

 are low; the crowns of some of the premolars have a cingulum in front 

 and behind. The canines are lost, but their alveoli indicate huge size ; 

 the root possesses an open groove on the front of the inner side. The 

 outer incisors large ; the last molar two-lobed and rather small. 



