254 



MICROTIN^ 



the sandy dress of the fully adult animal in winter there is a long 

 series of intermediate pelages, in the course of which the colour 

 is gradually changed, the mantle becoming at the same time less 

 diffuse and more evidently contrasted with the face and flanks. 

 Skull and teeth essentially as in E. r. rufocanus. The only 

 specimen before me in which the teeth are rooted is unfortunately 

 imperfect; in it the dental length is 154 mm., a dimension which 

 indicates probably a condylo-basal length of about 25-8. On the 

 other hand, in the three largest specimens (26-3-26-7) m^ is still 

 growing, as it is also in equal-sized skulls of E. r. regulus and 

 E. r. smithii, although in such equal-sized skulls of E. r. rufocanus 

 as are available, the teeth are in all cases rooted (see table at 

 p. 261). 



Fig. 84. — Evotomys rufocanus shanseins Thomas. 



Cheek-teeth of young specimen, one of the typical series of " Caryomys 

 inez" ; a. right upper, 6. left lower molars. 



For external and cranial measurements, see tables at end of 

 volume. 



Remarhs.- — As the synonymy given above indicates, "Caryomys'^ 

 and its five species have been based upon immature specimens of 

 E. rufocanus and the systematic history of this species in China 

 thus affords an exact parallel to its systematic history in Japan 

 (see p. 257 below), where the young were referred to a special 

 genus " Phaulomys " and the adults to " Craseoniys." 



After carefully comparing all the available material represent- 

 ing the five nominal species of " Caryomys " with the long series 

 from Japan hitherto referred to " E. {Phaulomys) smithii,'^ I can 

 find no character in either the skull or the teeth by which the 

 one series can be distinguished from the other. The " species " of 

 " Caryomys " differ from each other rather strikingly in colour, 

 but those differences arise also from differences of age, and even 

 the extremes find close matches in the " smithii " series from 

 Southern Jajian. The following details may be given : — 



(1) "Caryomys inez'': — Based on eighteen specimens collected 



