1871.] Proceedings of the Asiatie Society. 113 
The form of the shell of both is so variable that no importance 
can be attached to it, the only difference being, that the one of 
Cremnoconchus has a peculiarly thin texture, and that it is covered 
with a very distinct olivaceous epidermis. As to animals, Cremno- 
conchus differs from Littorina by the subcylindrical foot, the sole 
of which is only indistinctly grooyed, ayd by the males having 
the penis destitute of an appendage. There is no peculiar 
difference in the form of the teeth, except that each has 7 denticles, 
while in Littorina there are usually only 5 present. The operculum 
is also in both very similar, paucispiral and horny, only in most spe- 
cimens of C. Syhadrensis it becomes in time quite testaceous. 
For these reasons I believe, therefore, that Cremnoconchus can be 
regarded only as a subgenus of Zvétorina, and should be classed 
next to Risella (= Bembicium), the relative position of the lateral and 
central teeth being very similar in both. Of Zisella two species 
occur on the Arracan coast, at the Andamans, and Nicobars, 
Penang, &e. 
In my Monograph of the South Indian Gastropoda, (Palzont. 
Indica, II, p. 259, et seq.), I have divided the Lrrrorryipx into 
three sub-families, FossaRIN@, LACUNIN® and LirrorIniInz. Subse- 
quent researches make a thorough change in the classification of 
the family necessary. 
In the first named sub-family only Risella can be regarded 
as atrue Littorinid, and must be placed near Littorina. Fossar 
and its allies must be excluded from the present family. In 
the LAcunin® have provisionally to remain: Lacuna, Modulus, 
Stenotis, and Lacunaria, while Lithoglyphus is to all appearance 
a Rissoid form, and must be classed near Bythinia and Amnicola. 
The LirroRininZ® include Cyc/onema, Spironema, Amberleya, Echinella, 
Hamus, Risella, Cremnoconchus, Neritoides, and Littorina. Researches 
in fossil conchology may increase this list considerably. 
With regard to the relation of Cremnoconchus to Cyclostomus, 
Cyclophorus, and some of their allies, it is worth while drawing 
attention to the many points of similarity which exist between the 
Littorine in general and these operculated landshells. The ani- 
mals, and their dentition, are in both often extremely similar, with 
the exception that the former have the end of the muzzle truncate, 
while the Cycropnorm2 have it lobed. The operculum in Cyelo- 
