1903.] Allen, Mammals from Northeast Siberia 145 



12. Evotomys (Craseomys) latastei, nom. nov. 

 KAMCHATKA RED-BACKED MOUSE. 



Arvicola rufocanus variete" kamtschaticus LATASTE, Ann. Mus. Civ. 

 di Stor. Nat. di Geneva, XX., 1884, 284 (in text). The range here 

 given as "dans le Kamtschatka, sur les bords de 1' Armour, aupres du 

 lac Baikal, sur 1' Altai, et ge"ne*ralement, dans tout le nord de la 

 Sib6rie." Not Arvicola kamtschaticus Polyakoff, 1881. 



E. latastei differs from E. rufocanus in its much smaller size, 

 less angular teeth, rounder bullae, less fulvous underparts, and 

 darker gray sides. 



A series of 18 specimens (including two in alcohol) col- 

 lected at Gichiga, is provisionally referred to this species, the 

 type region of which is northern Kamchatka. In the ab- 

 sence of typical representatives of E. kamtschaticus any other 

 course seems inexpedient. 



The Gichiga series was taken as follows: Jan. 12, i; May 

 12, i; June 25, i; Aug. 27, i; Sept. 11-24, 14- The. January- 

 specimen is in very long, soft pelage, clear grayish white below, 

 the sides rather light clear gray, and the back yellowish rufous ,. 

 with numerous long black-tipped hairs. The May specimen 

 is in shorter, less full pelage, with the color much as in the 

 January specimen, except that the rufous of the back is more 

 dilute, through the less developed fur, but of the same tint. 

 The adult September specimens are darker, the sides being of 

 a darker gray, the ventral surface deep pure gray with a whit- 

 ish wash, and the back dark rufous or chestnut. Young 

 specimens about two thirds grown, partly in the soft woolly 

 pelage of the young, have the sides and lower surface practi- 

 cally as in September adults, but the back in one specimen: 

 (the youngest) is only slightly suffused with rufous, restricted 

 to the median region; in others, somewhat older, the rufous 

 is stronger and suffuses a broader area. 



The external measurements of 10 adults are as follows: 

 Total length, 128 (120-140) mm.; tail, 29 (24-33); hind foot, 19 

 (18-20). Six adult skulls measure as follows: Total length, 

 23.6 (22.5-25) mm.; basal length, 20.5 (19-22); zygomatic 

 breadth, 13 (12-13.8); nasals, 6.2 (5.7-6.5). 



[March, J<?oj.] 10* 



