148 THE MAMMALIA OF THE DEEP RIVER BEDS. 



The extreme fragility of the type specimen and the hardness of the cement-like 

 matrix in which it is imbedded have prevented the complete exposure of the teeth, 

 so that these can be studied only from the external side, and important questions as 

 to the constitution of their crowns must be left undecided. In the other specimens 

 of the species at my command, the teeth are so badly preserved as to be of no value 

 in this connection. The first and second upper incisors are very small, the lateral 

 much exceeding the others in size, and the second somewhat larger than the mediau. 

 These teeth, except for the greater relative size of the lateral one, closely resemble 

 the incisors of the immature skull mentioned above and referred doubtfully to Mes- 

 oreodon intermedins. The canine is of the type usual in the family. The premolars 

 have increased in vertical, but diminished in antero-posterior diameter; their front 

 and hind margins are nearly parallel and the acute apex in each tooth is in advance 

 of the median vertical line of the crown. Thus the postero-inferior cutting border 

 is longer than the antero-inferior. In Mesoreodon the apex is in the middle line and 

 the inferior trenchant margins are of subequal length. The molars exhibit the same 

 reduction in length (antero-posteriorly) and increase in height as do the premolars, 

 and arc almost as distinctly h} T psodont as are the molars of the later species of 

 Merycliyus from the upper Loup Fork. The external pillars, especially the. median 

 one (mesostyle), are thin and compressed, but very prominent. The postero-external 

 crescent is much more extended from before backward than the antero-external one, 

 though the disproportion is less than in Mesoreodon. 



The lower incisors are larger and, in particular, higher than the upper ones, and 

 have compressed chisel-shaped crowns ; the canine is broader than the incisors but 

 has lost its typical shape. The caniniform first premolar calls for no remark, as it 

 departs in no way from the shape common throughout the family. The second and 

 third premolars resemble those of the upper jaw in their reduced length and increased 

 height and in having their apices in front of the middle line of the crown. In p- 4 the 

 heel (metaconid) is very distinctly separated from the protoconid, but is relatively 

 smaller than in Mesoreodon. The lower molars are so concealed in the matrix that 

 little can be made out with regard to them. As compared with the corresponding 

 teeth of the older genus, they have shorter but much more decidedly hypsodont 

 crowns. 



Merychyus pariogonus ? Cope. 



Proceedings Amer. Philos. Soe., Vol. XXI, p. 542. 



In the Princeton collection is the facial portion of a skull, which was found by 

 Mr. Benet in the upper series of beds in the Deep River valley, and which clearly 



