400 
ZOOLOGY OF THE FAR EAST. 
expanded or plate-like ; the upper part sculptured with more or less obsolescent, 
thick spiral ridges, the lower part, below the periphery of the body-whorl, nearly 
smooth. 
Embryonic shell of relatively large size, subcylindrical, with the apex minutely 
blunted, the suture deeply and broadly depressed and each whorl bearing on its 
Fig. I. — Young shells of Heterogen tnrris. sp. nov. (nat. size), 
surface two prominent, smooth spiral ridges separated by a broad and deep concave 
region. 
Operculum rather thin, with an unthickened margin and a well-defined funnel- 
shaped concavity on the external surface, corresponding to a prominent boss on the 
internal surface surrounded by a thickened muscular scar. 
Nothing is known of the anatomy of the animal. 
Type-species. — Heterogen turris, sp. nov. 
Heterogen turris, sp. nov. 
The adult shell varies somewhat in outlines and proportions and two types, 
perhaps sexual, can be distinguished, in one of which (? the female, fig. 2A) the 
shape is less elongate than in the other ( ? the male, fig. 2B ). In both the upper 
part of the shell is conical but has the apical whorls invariably eroded. There are 
Fig. 2. — Adult shells of Heterogen turris, sp. nov. (nat. size). 
in all 6| or 7 whorls, or would be if the shell were complete, but as a rule only the 
last three remain perfectly intact. These whorls are often almost smooth except 
for the presence of rather fine but irregular longitudinal striae, but three obscure 
coarse spiral ridges can usually be distinguished on each. There is a well-defined 
