312 
ZOOLOGY OF THE FAR EAST. 
ate in front. The eyes are degenerate but are apparently represented by swellings at 
the outer base of each tentacle. The penis has a lateral branch ; the whole structure 
is very large, broad and somewhat flattened, the main trunk tapering, the lateral 
process, which is well developed, blunt at the tip. The dorsal surface of the head 
and foot are blackish, the tips of the tentacles black and that of the lateral branch 
of the penis white. 
The radula is of the Hydrobiid type, but approaches that of the Rissoidae in 
some respects. The central tooth is small ; it bears on its base, well within the mar- 
gin on either side, a pair of cylindrical processes ending in short spinelets ; the cusp is 
narrowly triangular, with a triangular process in the centre and two coarse denticula- 
tions at either side. The internal lateral tooth is broad ; its upper margin is armed at 
the inner edge with three bluntly pointed processes of which the innermost is much the 
largest; the remainder of this margin is coarsely, bluntly and evenly serrated. The 
outer lateral tooth is also broad ; its denticulations, which are confined to the upper 
margin, are minute, blunt and even. The marginal tooth is much narrower; its 
denticulations resemble those of the tooth next to it, but it bears a narrow, bluntly 
pointed process of considerable relative length at the outer extremity of the upper 
margin. All the teeth are rather small, delicate and of a pale yellowish colour. The 
whole radula is small and narrow. 
Type-specimen. No. M 10415/2, Zool. Survey of India {Ind. Mus.). 
Locality. Narrow creek at Tong Dong Ding, Tai-Hu, China. 
Three specimens of P. hypocrites were dredged from a depth of about 3 metres. 
They were apparently living among weeds on a muddy bottom. The specimen selected 
as the type-specimen and figured on pi. x is considerably more elongate and larger 
than the other two. It is an adult male. 
This specimen was obtained in December, 191 5. After remaining dry for some 
months in Calcutta it was sent to London. It was sent back to Calcutta in January, 
1918. When the operculum was removed recently the soft parts were found to be 
in excellent condition and still damp, after the shell had been dry for more than 
two years. The stout operculum is probably, therefore, of use to the animal, should 
the water in which it lives chance to dry up, in enabling it to store up moisture inside 
the shell for long periods. It is probable that the individual examined had lived out 
of water for at least two years, through the greater part of a hot weather in Calcutta 
and part of a winter in England. It must have died only a short time before I ex- 
amined it, if it were really dead. In a smaller individual, however, with exactly the 
same history the body was hard, dry and shrivelled. 
Family ASSIMINEIDAE. 
Genus Assiminea, Gray. 
Assiminea scalaris, Heude. 
1882. Assiminea scalaris, Heude, op. cit., p. 83, pi. xxi, figs. 5, 5.'? ^b, 5c. 
As Heude' s work is not always accessible I quote his description of the shell. 
"A. testa parva, perforata, subsoHda, cornea, vix striatula, carenis pluribus 
