380 PROCEEDINGS OF THE ACADEMY OF [1896, 



As compared with A. rutila of the northern parts of the earth, 

 this species has double the linear dimensions of the teeth. 



Measureynents. m.m. 



C longitudiual of crown ; 6 



Diameters of M. y I anteroposterior ; 4 



( transverse posteriorly ; 1.6 



J longitudinal of crown ; 5 



anteroposterior ; 2 



transverse posteriorly ; 1.5 



( longitudinal of crown ; 5 



Diameters of M. ^ <. anteroposterior ; 2 



( transverse posteriorly ; 1 



The teeth of the second specimen are a little larger than those 

 above measured. They are in a decayed jaw, with the incisor in 

 place, and they agree with the types in all details, excepting only 

 that the external column of the anterior lobe is not grooved. 



The first inferior molar, which was originally described and fig- 

 ured, is peculiar in the failure of the anterior triangles to isolate 

 themselves from each other. This character turns out to be incon- 

 stant, as in two other corresponding teeth the triangles are closed. 

 The name Anaptogonia was applied to the species in a subgeneric 

 sense, and although based on a worthless character, must, under the 

 rules, be retained. It antedates the Evotomys of Cones, which was 

 proposed in 1874 in the Proceedings of the Academy of Natural 

 Sciences of Philadelphia, p. 186, for voles with rooted molars. 



Anaptogonia cloacina Cope sp. nov. ^ 



Crowns prismatic, the common pulp cavity with lateral walls 

 which close the lateral grooves, but do not close the pulp cavities ; 

 no roots. 



The dentition of this species is that which is regarded by G. S. 

 Miller as that of the immature stage of the species which were termed 

 by Merriam Phenacomys. I do not see that this dentition can be 

 distinguished from that of Anaptogonia.'^ 



Two individuals of this species are indicated by the specimens 

 preserved by Mr. Mercer. These include, the first, the M. ^ and 

 M. - ; the second, the M. i and M. ^. As usual in this group, 

 the molars diminish in size posteriorly. The triangle formulae are : 

 M. -L, 1 I ; M. ^, 1 ^ ; M."^, 1 ^+3 lobes. 



2 North American Fauna, No. 12, 1896, p. 40. 



