156 Records of the Indian Museum. [Vor.. XVIII, 
basin of Seistan has been in all probability too recent for any very 
marked change to have taken place in their structure, and, as is 
so often the case when a fauna survives in abnormal conditions, 
structural peculiarities are on the whole less marked thana 
physiological vigour and a power of reproduction sufficient to 
overcome adverse factors in the environment. It is too often 
forgotten that physiological evolution may take place, and fre- 
quently does take place, without visible bodily change. 
DESCRIPTION OF THE FAUNA, 
All the fish in the fauna of Seistan belong to the suborder 
Cyprinoidea and to the families Cyprinidae and Cobitidae. Those 
representing the former family belong to the two subfamilies 
Cyprininae and Schizothoracinae. Three species fall in the Cobi- 
tidae, and three in each of the subfamilies of Cyprinidae. 
KEvY To THE FISHES OF SEISTAN. 
A. Scales of large or moderate size present on some part 
of the body ; posterior pharyngeal bones stout, bear- 
ing coarse teeth arranged as a rule in more than one 
row ; air-bladder large, free 
1. Lateral scales of large or moderate SES, much less 
than 100 in lateral line; no greatly enlarged 
scales in the region of the vent 
a. Lower jaw sharp, with an internal horny 
sheath ; no adhesive disk behind the mouth.. 
Scales 37-39%, 2 barbels ; diameter of eye 4 to 
Ax times in length of head, depth of body 3% 
to 3+ in total length e 
Ds ik ower Taw blunt, without a horny sheath ; an 
adhesive disk behind the mouth us 
i. Ventral surface covered with scales; 4 
barbels ; adhesive disk without posterior 
free border 
ii. Chest naked; 2 barbels; 
Cyprinidae. 
Cyprininae. 
Scaphiodon. 
S. macmahont. 
Discognathus. 
pas . D. adiscus. 
posterior border 
of adhesive disk free D. phryne. 
2. Jateral scales, if present, small, more than 100 in 
the lateral line; a sheath of greatly enlarged 
scales in the anal region Schizothoraci- 
a. No lateral scales ; a scapular patch of enl arged nae, 
scales. present; no barbels; lower jaw 
sharp Schizopygopsts. 
Mouth extending backwards nearly as far as 
or slightly bey ond the anterior border of the 
eye; pectoral fin much shorter than head ,,, 
b. \ateral scales present. 
i. Mouth terminal or subterminal, lower jaw 
blunt; ventral scales present; 4 bar- 
bels : 
Scales at base of fins slightly enlarged ; 
anal sheath rather poorly developed ; 
S. stoliczkae. 
Schizothorax. 
lips normal 
11. Mouth ventral ; 
scales absent ; 
sent 
Origin of dorsal equidistant from eye and 
base of caudal, above posterior part of 
pelvic shin 
lower jaw sharp, ventral 
barbels vestigial cr ab- 
S. zavudnyt. 
Schizocypris. 
S. brucei. 
