1919. | N. ANNANDALE & B. PrasHaD: Mollusca. 49 
The jaw and radula are of the same type as those of the species 
already discussed, and closely resemble those of L. bactriana in 
particular. They exhibit, however, great placticity and individual 
variability (see figures, p. 42). The marginals never have the pecu- 
liar form of those of L. ivanica. 
Genitalia. The genitalia are of the same type as those of L. 
bactriana, but have one important difference, viz. that whereas in 
that species the male and female parts of the system are approxi- 
mately equal in length, in L. gedrosiana the vas deferens is greatly 
elongated, while the female ducts are short. This difference is not 
correlated with any difference in the position of the external sexual 
apertures, which in both species are situated almost on a level, but 
in L. gedrosiana the male duct is strongly convoluted. 
Type-specimens. M. 11533/2, Zoological Survey of India 
(Ind. Mus.). 
Localities. ‘This species is common, as Hutton noted, in the 
Pishin district (Chaman) and at Kandahar. It also occurs in abun- 
dance at Quetta and in the Hamun-i-Helmand in Seistan. 
Habits. L. gedrostana can apparently live only amidst dense 
submerged vegetation. Hutton found it in brick tanks at Kanda- 
har and ina small marsh at Chaman. Our specimens from Quetta 
were taken among weeds in a pool supplied by water from 
an underground source in the Residency gardens. The submerged 
vegetation in this pool was dense and the water, in November and 
January, perceptibly warmer than the air. In the Hamun this 
Limnaea occurs mainly amidst algae growing on the roots of 
Phragmites and also on Potamogeton pectinatus in small pools in the 
reed-beds. 
Affinities. L. gedrosiana is apparently related to L. peregra, but 
differs in the blunter spire, more oblique spiral and longer mouth 
of its shell. We do not feel justified in uniting the two forms, and 
the shell differs considerably from that of any of the ‘‘ varieties”’ 
from Central Asia ascribed to L. peregra by former authors. 
Variation and plasticity. There is not much individual varia- 
tion in shells from the same environment, except that correlated 
with age. Shells from Quetta, however, are larger and a little 
broader and have distinctly larger mouths than those from the 
Hamun. Moreover, their spire is distinctly shorter. 
var. rectilabrum, nov. 
(Pl. vi, figs. 1-6.) 
This variety or phase differs from the forma /ypica so far as the 
shell is concerned mainly in having the outer lip distinctly flattened 
so that it slopes outwards in a straight line. Its margin is some- 
times slightly turned inwards towards the aperture. The precise 
form of the mouth is, however, subject to considerable individual 
variation (see pl. vi). The radula does not differ more from that 
of the forma typica than that of the latter varies. The genitalia 
