314 
ZOOLOGY OF THE FAR EAST. 
to that species or to V. angulata (Miiller) in the rounded and more or less flattened 
apex of the shell. This feature is concealed to some extent by erosion in all the 
adult shells I have examined, but is well exemplified in young shells from the 
Tai-Hu. 
Specimens from the Tai-Hu and Soochow differ from Heude's figures in their 
smaller size and rather greater relative breadth of shell. They vary, however, con- 
siderably in the latter character. I give measurements (in millimetres) of three speci- 
mens. 
Length. Breadth. Aperture. 
19-5 14-0 9-5 X 7-0 
2I"5 14-5 IQ-O X 7-0 
19-0 13 5 9-25 X 7-25. 
The shells also vary in the number of spiral ridges and their relative develop- 
ment. In some the epidermis covering the ridges is frayed in such a way as to 
form rows of "cilia ", and in others these structures assume the appearance of micro- 
FiG. 6. — Radular teeth of Vivipara lapillorum. 
scopic spines. In some, however, there is no trace of any such peculiarity. The 
epidermis is of a pale green colour, with occasional longitudinal blackish streaks. 
The margin of the aperture is sometimes blackish. The shells have a distorted and 
dwarfed appearance doubtless due to some peculiarity of their environment. The 
surface even in quite young individuals is always eroded. 
The operculum is thin and horny but of a very dark brown colour. It is rather 
narrowly pyriform and has the posterior extremity bluntly pointed and very 
slightly retroverted. The outline is almost bilaterally symmetrical. The external 
surface is concave as a whole and surrounded with several concentric ridges. The 
internal scar is relatively large. 
The radular teeth (fig, 5) are large and of a yellowish colour. The denticulation 
of the lateral teeth is unusually coarse and well-developed. 
This dwarfed phase of V. lapillorum is common on stones and bricks at the 
edge of the Tai-Hu and also in canals at Soochow. Heude's statement as to the 
type locality and habitual environment of the species is by no means clear. 
