LAGOMOEPHA. 883 



several hundred specimens of the former species I obtained twenty of this 

 one, inchiding both dental series and their supporting bones, and various 

 portions of the skeleton, but no cranium. 



The maxillary bone displays the fossa below the anterior base of the 

 zygomatic arch much better defined than in the P. haydeni. The palatine 

 bone extends to the same distance forwards, that is, to opposite the anterior 

 border of the third molar. The portion of the bone at the side of the pos- 

 terior emargination is nan-ower, and not so horizontal as in the P. haydeni. 

 The notch has the same extent, viz, to the line of the posterior border of 

 the fourth molar. 



The superior molars are similar in general to those of the P. haydeni, 

 but in none of them do I observe the fissure of the inner side of the crown. 

 In several of them the median crescent persists, so that if the internal fissure 

 exist at any time it must be speedily removed by attrition. In P. haydeni 

 it remains after the disappearance of the crescent, as in that species there 

 is no enamel on the external side of the crown. 



The mandible is more robust than in P. haydeni, but has much the same 

 form. The anterior mental foramen is behind the middle of the diastema, 

 on its superior aspect, and the posterior is below the second molar, below 

 the middle of the ramus. The dental foramen is above the middle line of 

 the ramus; the last-named two foramina having relations the reverse of that 

 seen in P. haydeni. The anterior border of the masseteric fossa is ele- 

 vated into a prominent rough ridge in most specimens, and reaches to the 

 penultimate molar. The tuberosity inclosing the incisive alveolus does not 

 extend so far posteriorly as in P. haydeni, ceasing below some part of the 

 second molar, varying a little in different individuals; its surface is covered 

 with impressed punctse. The anterior border of the pterygoid fossa of the 

 ramus is not well defined. 



There is no groove on the inner side of the first molar. The two col- 

 umns of the three intermediate molars are closely appressed, and the second 

 is lower, not so wide, but a little longer anteroposteriorly than the anterior 

 colvimn. The last molar is deeply grooved on the inner side; its grinding 

 face is only half as large as that of the first molar. The inferior incisor is 

 not deeper than wide, and is obtuse behind. The anterior face is nearly 



