cave to tb e anterior extremity of the crest, which slopes upwards. The 

 incisive alveolus, though not prominent as in the Hystricomorpha, is on the 

 inner side of the hase of the ramus in front, and the enamel-face of the 

 incisor tooth is directed more inwards than downwards. Ahove the alveo- 

 lar prominence, the inner face of the ramus is gently concave. The ante- 

 rior origin of the coronoid process is opposite the posterior border of the 



second molar. 



Measurements. M. 



Length of inferior molar series 0105 



Width of anterior face of inferior incisor 0028 



Depth of ramus at M. 2 0085 



Width of ramus below at M. 2 0070 



Pletjrolictjs suxcifrons, gen. et sp. nov. 



Char. gen. Fam. Saccomydiee. Superior molars rooted and short-crowned. 

 The crowns with a lateral fissure bordered with an inflection of the enamel 

 sheath, extending to their bases. In the superior molars this inflection is 

 on the external side, and does not dividethe crown. Superior incisors not 

 grooved. 



This genus is curiously near to the existing Heteromys and Perognathus, 

 the two genera of Saccomyidw with rooted molars. The former differs in 

 having the molars divided into two columns, each of which is sheathed in 

 enamel, while Perognathus only differs so far as I am aware, in having the 

 superior incisors grooved. 



Specif. Char. This species resembles those of the allied genus Entop- 

 tychus in many respects. The superciliary borders are thickened upwards, 

 forming two ridges, which enclose a groove between them which is more 

 pronounced than in the Entoptychus cavifrons. The muzzle is plane above 

 and considerably wider than the interorbital space. The base of the ma- 

 lar is thin and oblique, and the foramen infraorbitale exterius is well in 

 advance of the molar teeth and at the anterior part of the maxillary bone. 

 A groove passes backwards from its inferior border, terminating in a small 

 foramen which marks a point nearly half way to the first molar. Within 

 this, another shallow groove bounds the more prominent median line. The 

 palatal surface exhibits two shallow lateral grooves, which commence op- 

 posite the posterior border of the first molar. 



The grinding surfaces of the molars are transverse ovals, only interrupted 

 by the exterior fissure. The first molar is slightly different in form, being 

 larger, and its section, when not much worn, being nearly round. Its an- 

 terior portion extends towards the alveolus, giving an antero-posterior oval, 

 on prolonged wear. Each tooth has three roots, one interior and two 

 exterior ; in th« first they may be described as two posterior and one ante- 

 rior. The last mojar is the smallest, the series exhibiting a regular grada- 

 tion in size. 



Measurements. M. 



Interorbital width 0050 



Width of muzzle at middle 0080 



