1920.) N. ANNANDALE & S. L. Hora: The Fish of Seistan. 169 
constriction. The pneumatic duct is long and slender and opens 
into the posterior part of the bladder just behind the constriction. 
In Schizothorax zarudnyt the weberian ossicles closely resemble 
those of so different-looking a Cyprinid as Labeo rohita, to which 
one of us has recently devoted special study in reference to these 
bones. The alimentary canal also is closely similar in the two 
fish. 
There is a strong probability that the Central Asiatic sub- 
family is related to the Labeo section of the Cyprininae, from 
which it has been derived as a result of isolation in mountain 
rivers flowing rapidly at high altitudes. An important factor, 
TExtT-FIG. 5.—Scales of Schizothoracinae. 
a. Dorso-lateral scale of Schizothorax zarudnyt, X 17%. 
6. Dorso-lateral scale of Schizocypris brucei (adult specimen), X 373. 
c. Anal scale of Schizopygopsis stoliczkae from Siestan, X 17}. 
noticed by Stewart! in Tibet, is probably the necessity for long 
and arduous migrations at different periods of life. 
The three species (each of a different genus) that live in the 
lowlands of Seistan are either identical with or very closely related 
to mountain forms, but, as we have already noted, their isolation 
in a depression has not produced any very noteworthy structural 
modification of a general kind, perhaps because it is still too recent. 
1 Stewart, Ree. Ind. Mus., V1, p. 73 (1911). 
