248 Mammals of Eastern Asia 
white. The tail is gray, its tip dusky. The ears have no basal 
tufts of hairs. The cheek teeth are not greatly complicated. The 
number of nipples is 8. The length of the head and body is 6% 
inches, tail 4% inches, hind foot 1% inches. 
This group of Flying Squirrels is found from Russia across 
northern Asia to Siberia and south along the coast of the Pacific 
to northern China. The following races are shown by Ognev to 
inhabit the coastal portions of eastern Asia : P. v. anadyrensis, 
extreme eastern Siberia near the base of the Kamchatka Pen- 
insula; P. v. incamis, Siberia, north of the Sea of Okhotsk to 
beyond the Arctic Circle and westward to the Yenisei River; 
P. v. athene, the west coast of the Sea of Okhotsk, Sakhalin, 
and Yezo (= Hokkaido) Islands, and Maritime Province of 
Siberia south to lat. 45°; P. v. arsenjevi, the southern part of 
the Siberian Maritime Province and eastern Manchuria to the 
north shores of the Gulf of Pechili and northern Hopei ; P. v. 
momonga, Japan, excluding Yezo; P. v. aluco, Korea, Hopei, 
Shantung. Allen admits two other races : P. v. buechneri from 
Kansu, China, and P. v. wuhmgshanensis from Mt. Wuling 
(Wulung), southern Jehol. The Pteromys of Hokkaido, Japan, 
have been divided into several local races. 
The Arrow-tailed Flying Squirrels, Hylopetes, closely re- 
lated to Pteromys and perhaps only a subgenus, have the tail 
broad and feather-shaped. The audital capsules are enlarged. 
The number of nipples is 6 (Thomas). The typical species is 
H. everetti of the Natuna Islands. The genus, widely distributed 
from Burma and Laos to the Sunda and Philippine Islands, 
can be separated into two size groups : the typical small-sized 
everetti, sagitta, and phayrei, and the considerably larger 
alboniger and leonardi. 
Hylopetes sagitta, recorded first from Java, is shown by 
Chasen to be represented on the Malay Peninsula by H. s. 
platynrus and in Arakan and northern Malay by H. s. spadiceas. 
Hylopetes s. platyuriis has the upper surface clothed with 
