63 
is gone over it is regularly found to contain many specimens 
which are impossible to determine according to the definitions 
given. The average of a set of examples from Central Asia 
and Eastern Asia, or from China and Japan, differs suffi- 
ciently to have justified the earlier authors in establishing 
the several species, but, the number of specimens found with 
intermediate characters absolutely precludes the possibility 
of retaining these names as indicating valid species. 
In reviewing the literature one may read in the volume 
by Strauch, “So halt es nicht ganz leicht, ein Merkmal za 
finden, durch welches sie fur alle Falle mit Sicherheit von 
einander zu unterscheiden waren.” (1). Boulenger in speaking 
of A. intermedius states that it “Agrees in most respects with 
A. halys, but the snout is not at all turned up at the end, as in 
A. blomhoffii’; and A. blomhoffii he mentions as “Closely 
allied to A. halys, with which it agrees in most respects, but 
the snout not turned up at the end, and scales more strongly 
keeled” (2). Professor Leonhard Stejneger writes: “It will be 
seen that a considerable amount of intergradation occurs. Thus 
it would be impossible to say to which of the three forms 
(Tables II, III, or IV) a specimen with 151 ventral and 45 sub- 
caudals were to be referred unless it had 8 supralabials, * (3). 
From this it may be inferred that these authors have felt 
the inherent difficulty of separating these forms. 
When it is admitted that one form agrees in most respects 
with another, that it is difficult to find a character that will 
separate them, and that considerable intergradation occurs, 
the probability is that but one valid species is under considera- 
tion. It is also fairly certain that further collecting along the 
zones of contact of the two supposed forms will bring to light 
Many specimens with the intermediate characters necessary 
to cement the two groups into a single species that henceforth 
will be of increased interest owing to its range of variation. 
This, it is believed, is the status of Ancistrodon halys. 
VARIATION IN NUMBER OF VERTEBRAE. 
There are many members of the sub-order Serpentes that 
show a vastly greater variation in the number of verterbre 
than do any of the other animals in the entire Phylum of 
Vertebrata. An extreme example of this nature is the Marine 
Serpent Distira fasciata (Schneider) 1799, the number of 
(1) 1873 Strauch, Schl. Russ. R. p. 235. 
(2) 1896 Boulenger Cat. Sn. Brit Rigs Roe pp. 525-526. 
M. p. 452 
(3) 1907 Stejneger, Bull. No. 58, U 
