208 VERTEBRATE REMAINS, PORT KENNEDY BONE DEPOSIT. 



Measurements. 



mm. 

 Length, grinding surface infer, molars (no. 1) ; 6.5 



Length, grinding surface 1st infer, molars (no. 1) ; 3.0 



Length, fang and crown infer, molars (no. 1) ; 4.0 



Width, inferior incisor; 1.5 



The supposed superior maxillary dentition is represented by both series, that 

 of the left side lacking the first molar, with the palatine surface and one upper 

 incisor. The lobe formula is If, 1^, 1^ 1 three lobed. The lobe of the posterior 

 molar is quite elongate, and divaricates into two angles anteriorly, the external 

 of which is almost isolated, almost giving the formula for the tooth 1^ 1. The 

 teeth of both sides are almost exactly alike. The near approach to isolation of 

 this external angle is due to the deep inflection of the posterior inner groove and 

 very near approach to a corresponding incurvature of the lobe. 



Measurements. 



mm. 

 Length of dental series ; 7.0 



Width between middle of mm. 2 ; 5.0 



Width incisor tooth in front; 1.5 



Length from m. 2 to incisive foramen ; 4.9 



MlCROTUS INVOLDTUS Cope. 



Arvicola involuta Cope, Proc. Am. Phil. Soc, 1871, p. 89, fig. 16. 



This species is represented by a mandibular ramus which supports all the teeth. 

 The triangle formula is : (1) 1 + \ 1 ; (2) 1 \ 1 ; (3) 1-1-1. The trefoil is of 

 peculiar shape, which distinguishes the molar from the corresponding one of 

 M. dide/tus, to which this species is nearly allied. The two basal open triangles 

 are present, and anterior to these are two angles which are not opposite, and one of 

 which is much more prominent than the other. Anterior to these there is no lobe 

 such as is characteristic of the species of Microtus generally, but the anterior border 

 passes from one angle to the other. As one angle is much more prominent than 

 the other, and is more anterior, the resulting figure is a hook, of which the more 



prominent angle is the point. 



The m^ is characterized by the complete fusion of the two opposite anterior 

 triangles, which is as complete as M. pinetorum, though the angles which represent 

 their apices are not quite opposite. The sections of the columns of the nig- are 

 acute angled triangles attached near their bases, and well isolated. 



Measurements. 



mm. 



Length of inferior molar series ; 6 



Length of m T : 2.5 



Width of m T posteriorly ; 1 



Length of m ¥ . 1.5 



Width of m ¥ posteriorly ; 1 



