6 



The external faces of the external tubercles of these teeth are somewhat 

 flattened. The first premolar has one root, the others have two. They are 

 equidistant and not very closely crowded. 



Several suillines are described by Marsh and Leidy, either imperfectly or 

 from imperfect material, so that I have had some difficulty in determining 

 my specimens. The D. hesperius of Marsh is probably, as above observed, 

 a Chmnohyus. I have specimens agreeing with Marsh's description of 

 ThinoJiyus socialis. They belong to an animal of the size of the Chceno- 

 hyus decedens, but the superior molars have no basal cingulum. Its generic 

 position is yet uncertain. Other specimens agree in characters with the 

 Dicotyles pristinus of Leidy, with which Thinohym lentus of Marsh agrees 

 in size. In this hog there is no diastema in front of the third inferior 

 premolar, so that it is clearly distinct from the Thinohyus triohcBnus of 

 the present paper. 



Mekycopateu guiotianus Cope. 



Having obtained several crania of this species, I can give the characters 

 of the genus Merycopater* more fully than hitherto. Dentition ; I. J-j a ; 

 C. \ ; P-m. \ ; M. f. A diastema above and below ; fourth superior pre- 

 molar with two external crescents ; fourth inferior premolar identical 

 in form with first true molar ; the first inferior premolar functionally the 

 canine. Orbit open posteriorly; no facial fossse or vacuities. 



This genus is Agriochcerus, with a considerable diastema, and very much 

 reduced superior premaxillary" teeth. In my best preserved cranium there 

 is no alveolus for the first ; that of the second is rudimental, and that of 

 the third is small. The premaxillary bones are very small and distinct 

 from each other. The enlargement of the cingula represents the posterior 

 internal tubercle of the fourth superior premolar, so distinct in Uoloreodon. 



The deficiency in superior incisors is an interesting approximation to 

 true ruminants not heretofore observed in Oreodontidce. I have found the 

 inferior incisors deficient in the genera Cyclopidius and Pithecistes. 



Colokeodon ferox, gen. et sp nov. 



Char. gen. Dentition, I. ? ; C. 1 ; P-m. 3 ; M. 8 ; a wide diastema 

 above ; the first inferior premolar functionally the canine. Last superior 

 premolars with two external and two internal crests Orbit open poste- 

 riorly ; no facial fossa? or vacuities. The genus differs from Agriocharus 

 in the wide diastemata, presence of but three superior premolars, and two 

 inner tubercles of the fourth premolar. 



I possess two species of this new genus, which are represented in my 

 collection by crania without premaxillary bones and mandibles. 



Char, specif. Size of Oreodon culbertsoni. Maxillary bone excava'ed 

 above the diastema, the superior border of the concavity extending nearly 

 to the base of the zygoma. Zygomatic arches expanded, their external 

 face concave below the orbit, and plane posteriorly. Saggittal crest very 

 high, dividing anteriorly into two ridges, which diverge widely, and 



* Cope, Americm Naturalist, 1S79, p. l l J7. 



