110 



even the first molar tooth. In the rabbits the defining ridge is comparatively 

 far back, extending only to the position of the interval of the last two molars. 

 In Paramjs it holds an intermediate position, extending as far forward as the 



position of the third molar, where it forms a conspicuous angular prominence', 

 as in the marmots. 



The mental foramen, much higher in relative position than usual in rodents, 

 is situated in advance of the molars a short distance below the edge of the 

 hiatus separating the latter from the incisor. 



Paramys delicatus. 



The largest species of Paramys was, perhaps, about a fourth less in size 

 than the Maryland marmot, though its series of molar teeth is nearly equal 

 in size, measuring three-fourths of an inch in length. It is represented by 

 two specimens sent to me by Dr. Carter, consisting of portions of the right 

 and left sides of the lower jaw, containing most of the molars and portions of 

 the incisors. One of them is represented in Fig. 23, Plate VI, of the natural 

 size. The triturating surfaces of the molars of both specimens, magnified 

 three' diameters, are represented in Figs. 24, 25. 



In. one of the specimens, Fig. 23, two mental foramina exist, one in the 

 position, previously indicated, in advance of the molars, a short distance 

 below the edge of the jaw ; the other is situated lower down below the posi- 

 tion of the first molar. In the other specimen the foramen exists in the lat- 

 ter position, and a's the jaw is broken in advance, it cannot be determined 

 whether a second existed, which is, however, probable, as it is the usual and' 

 normal position of one. A prominent tubercle is formed at the angle of con- 

 vergence of the ridges which define the masseteric fossa. 



Paramys delicatior. 



A second species is indicated by a specimen consisting of the greater por- 

 tion of the left ramus of a lower jaw, represented in Fig. 26, Plate VI. It 

 retains the second molar tooth, the triturating surface of which, magnified 

 three diameters, is represented in Fig. 27 of the same plate. The molar 

 series has measured about 1\ lines in length, and the animal was about the 

 size of our common gray rabbit. 



Since writing the above, I have received from Dr. Carter several additional 

 specimens which I suspect belong to the same species. One of them, an in- 

 termediate lower molar, is represented in Fig. 16, Plate XXVII. It suffi- 



