1919.] N. ANNANDALE & B. PrasHaD: Mollusca. 55 
not been for certain differences in the radula and for the fact that 
the habits are to some extent distinct. The shell, as one of us has 
pointed out (op. cit., 1918), differs from that of G. convexiusculus 
not only, as Hutton noted, in being more compressed and more 
strongly carinate, and having the lip and whorls of a slightly 
different shape, but also in being larger, more opaque and more 
coarsely and irregularly sculptured. The last whorl moreover as a 
rule deviates from the spiral of the upper whorls. These charac- 
ters are to some extent variable, but the radula differs in having 
all the teeth narrower, all the laterals tricuspid and the marginals 
with smaller cusps. The genitalia have all the ducts longer than 
those of L. convexiusculus and the spermatheca much larger. 
Otherwise they are very similar. 
(9 19 09,99 9 [ho 
pPrepPperur 7 VA 
Fic. §.—Radular teeth of Planorbidae. 
A. Teeth of Gyraulus euphraticus, Mousson, from Quetta (<5 700): 
B. Teeth of G. convexiusculus, Hutton, from the same locality (x goo). 
C. Teeth of Segmentina calathus (Benson) from swamp near Gurdaspur, 
Punjab (very highly magnified). 
Germain! regards Hutton’s Planorbis compressus as synony- 
mous with P. saigonensis, Crosse and Fischer, but specimens from 
Northern India have the sculpture coarser and more irregular, the 
last whorl more oblique, the mouth larger and more oblique and 
the inner whorls more concave on the lower surface than is shown 
of G. saigonensis in Crosse and Fischer’s? original figure, with 
which specimens agree. Specimens of the carinate form from 
Quetta, however, agree closely with shells of Mousson’s G. devians 
var. euphratica recently collected by Captain C. L. Boulenger in 
Mesopotamia. The species would, therefore, appear to be essen- 
tially a Palaearctic one, but there has been much confusion as to 
eee ee ee ee 
! Rec. Ind. Mus., Ul, p. 117. 
2 Crosse and Fischer, Fourn. de Conchyliologie, XI, p. 362, pl. xitl, fig. 7. 
