INTERRELATIONSHIPS OF GENERA 



65 



consist chiefly of more or less fragmentary jaws and isolated 

 teeth, representing three or four species, and do not throw any 



Microtu8 (Slenocranius) ravidulus Miller. 



Dorsal, ventral, and lateral views of skuU, enlarged ; the small figure 

 shows the skull in dorsal view, natural size. 



particular light upon the ancestry or relationships of the genus. 

 It is more convenient to reserve the discussion of the various 

 subgeneric groups into which the numerous species of Microtus 



V.L. F 



