828 THE JOHN DAT FAUKA. 



Meniscomys hippodus Cope. 



Paleontological Bulletin, No. 30, p. 5, December 3, lb78. Piocecdiiigs Amer. Philos. Soc. 1878 ('79), p. 67, 



Plate LXIII ; figs. 7-10. 



Superior molars with a vertical ridge from the points of junction of the 

 crescents on the external side; there are thus two on the second molar, and 

 one each on the third and fourth. Within each of the external crescents is 

 another crescentic edge of a pair of vertical enamel plates, and the inner 

 marginal crescent sends off a short'transverse branch towards them. With 

 attrition, all these crests unite by their extremities, inclosing four distinct 

 lakes, which, after still further wear, disappear. The crowns of the inferior 

 molars, in the unworn condition, terminate in two crescents; that is, in 

 elevated anterior, external, and posterior borders, with a transverse rMge 

 equally dividing the space thus marked out and joining the notch in the 

 external crest. This pattern resembles somewhat that of AncMfherium. 

 The first inferior molar differs from the others in its superior size, and in its 

 liaving the crescents more widely separated by a deeper external emargi na- 

 tion On attrition, the spaces bounded by the enamel crests are inclosed 

 hj the junction of the extremities of these crests on the inner side of the 

 crown. Further attrition results in three lakes within the crown, and one 

 notch of the external border and two notches of the internal border. The 

 anterior molar has two lakes in its posterior area, and one large one in its 

 anterior area. In old teeth there are, successively, one and no lakes left to 

 interrupt the dentine The first temporary molar (Pm. 2) has much the 

 form of the permanent tooth, but is smaller. The inferior incisor has a 

 Tvide, shallow groove or concavity on its external face. Superior incisors 

 regularly convex. 



The skull of one specimen shows that the otic bullae are large and 

 moderately compressed. They have no recurved lip at the meatus, and 

 their internal surface is covered with fine inosculating septa, forming a 

 reticulate pattern (fig. 7). On another skull I observe that the fronto- 

 nasal and fronto-maxillary sutures are in one transverse line, crossing the 

 iskull just anterior to the anterior border of the orbit. 



The maxillary bone, anterior to the molar teeth, is shorter than the 

 liremaxillary. The incisive foramina are entirely in the latter. The sides 



