Cope. J 4oO [Sept. 17, 



the inner lobe of the fourth superior premolar of the ruminants. The 

 general character of the true molars is that of Phenacodus. Parts of two 

 or three individuals of this species have come into my possession, one of 

 which includes nearly all of the molar dentition of both jaws. The 

 external cusp of the superior premolars is compressed conic, and the in- 

 ternal cingulum extends to its anterior base in the second, third, and 

 fourth. The crown of the last true molar is about as long as wide, while 

 that of the first is wider than long. Each supports seven cusps ; two 

 subconic external, and one large median internal, which is connected by 

 ridges with a small anterior and posterior median. Then there are a small 

 anterior and posterior internal, making three internal. The internal crest 

 is distinct from the principal cusp in the inferior premolars III and IV, 

 but unites with it in the II ; it supports on the IV an anterior, a median 

 and a posterior cusp, the latter forming part of the rather narrow heel. 

 The true molars I and II have seven tubercles, the four principal ones, 

 and three smaller, one anterior, one posterior, and one median. On the 

 third the posterior forms a large heel. All of the molars, but especially 

 the premolars, have the enamel thrown into sharp vertical parallel folds, 

 in a manner I have not seen in any other mammal. Length of six superior 

 molars .067 ; length of three true molars .029 ; length of base of third 

 premolar .012 ; width of do. .012 ; width of base of first true molar .010 ; 

 do. of third true molar .009 ; length of do. .010. Length base fourth 

 inferior premolar .012 ; width do. .010 ; length of third true molar .0115 ; 

 width of do. .009. The teeth indicate an animal of the size of the 

 peccary. 



Anisonchus sectoritjs, gen. et sp. nov. Char Gen. This is derived 

 from the superior P-m. IV and M. I and II, and from all the inferior mo- 

 lars of three individuals. The superior teeth are accompanied by a ramus 

 mandibuli, which contains alveoli of all the inferior molars, and the 

 crowns of the P-m. IV and M. II. The leading characters have been 

 given above. The inner posterior lobe is more prominent in this genus 

 than in any of the others, and has a V-shaped apex. It projects further 

 inwards than the anterior inner lobe. It is represented by a mere tubercle 

 of the cingulum in Miodomus. In the lower jaw the last premolar is quite 

 simple, consisting of a principal cusp, and a non-cutting heel. The 

 second true molar has intermediate anterior and posterior cusps. The ge- 

 nus differs from Pantolestes in the more numerous tubercles of the molars, 

 and in the fact that the anterior inner tubercle of the true molars is not 

 double. It may, however, be allied to that genus. 



Char. Specif. The fourth superior premolar covers a larger base than 

 either of the true molars. The external cusp has a base extended antero- 

 posteriorly, but the apex is conical, and there are no basal tubercles. The 

 inner cusp has a crescentic base as in GatatJilceus, but the apex is nar- 

 rowed and compressed conic. The external tubercles of the true molars 

 are subconic, and do not develop any external ridges. They are connected 

 by the crescentic slightly angular crest, whose apex forms the inner ante- 



