62 
The primary object of this contribution is to call atten- 
tion to the variation which may be exhibited by a single spe- 
cies of serpent. 
The data upon which the study of Ancistrodon halys 
(Pallas) is based have been derived from over two hundred 
specimens; nearly one-half of these have been examined and 
the records of the remainder compiled from literature. 
This species is of considerable interest, for with the ex- 
ception of Vipera berus (Linneeus) 1766, it has a wider dis- 
tribution than any other Solenoglyph. In fact, in this respect 
it is equaled by few members of the entire sub-order Ser- 
pentes. In general terms it is distributed from the Caspian 
Sea to Japan, and from Lake Baikal to the Kuen Lung System 
of Mountains. Definite localities on the outskirts of this area 
are: to the north, the Yenisei Valley and the Amur Valley; to 
the east, the Tschargan River and the Talysch District of the 
Transcaucasus; to the south, the Elburz Mountains, Lob Nor, 
and the Nan-shan Mountains, and to the west, the Ussuri 
Province, Japan, and Chekiang Province. The literature con- 
tains a few records of specimens from localities beyond this 
region (1) which are not sufficiently confirmed to be included 
at the present. 
Associated with this wide distribution there occurs a 
large range of variation. These two factors have been re- 
sponsible for the several supposed species that have been de- 
scribed in the past and maintained up to the present time. 
The series of specimens available for study has lead to the 
conclusion that the synonymy of Ancistrodon halys (Pallas) 
1776, should include the following: 
Ancistrodon blomhoffu Boie 1826, Japan. 
Agkistrodon blomhoffit brevicaudus Stejneger 1907 
Fusan. 
Ancistrodon affinis Gray 1849, type locality un- 
known. 
Ancistrodon intermedius Strauch 1868, Irkutsk. 
The prohibitive difficulty of maintaining these as dis- 
tinct species is due to the fact that when a real museum Series 
(1) Loo Choo: 1896, Boulenger, Cat. Sn. Brit. Mus. III, p. 526, (A. blomhoffii). 
1907, Stejneger, U. S. N. M. Bull. 58, p. 461, (A. blomhoffil affinis.) Formosa; 
1868, Swinhoe, Ann. Mag. Nat. Hist. (8), XII, p. 225, (Halys blomhoffil). 
Hainan: 1866, Bocourt, Nouv. Arch. Mus. Paris, II, Bull. ip. 9, (Trigonocephalus 
blomhoffii). 
Sinee these accounts have been published over three thousand reptiles and 
amphibians have been added to museum collections from these localities with- 
out additional specimens of this form having been taken. 
