240 LITTORINID®. 
fold, but differs in its fusiform outline, narrow aperture, and 
distinct canal. In its general appearance resembles Fascio- 
laria, but has only one instead of two or three columella-folds, 
and is destitute of ornamentation, and its outer lip is smooth 
within. 
CrypropLocus, Pictet and Campiche, 1854. 
Htym.—Cryptos, hidden, ploce, a plait. 
Distr.—T sp. Jurassic and Cretaceous; France, Switzerland, 
Germany. C.monilifera, d’Orb. 
Shell as in Nerinza, without columella and labial plaits; one 
plait on the posterior face of the aperture, a disposition very 
analogous to that in some Cerithiums, such as C. nodulosum ; 
aperture rounded, not channeled in front; umbilicated or im- 
perforate. 
Aptyxis, Zittel, 1873. 
Syn.—Pachystylus, Gemmellaro, 1878. 
Distr.—A. sexcostata, A’Orb. Jurassic. 
Shell turreted, nearly cylindrical, not umbilicated; mouth 
lengthened quadrangular; inner and outer lips without folds ; 
columella with a median fold-like thickening. 
Famity LITTORINIDA. 
Shell spiral, turbinate or globular; peritreme entire, interior 
not nacreous. 
Operculum corneous, spiral or paucispiral. 
Animal having a proboscidiform head with terminal mouth, 
and conical tentacles, subulate, with eyes at their outer bases. 
The species inhabit the sea, brackish or fresh water, some being 
amphibious. They are mostly littoral, feeding on alge. Den- 
tition (xi, 26). 
LitrorRiIna, Ferussac. 
Htym.— Littoralis, belonging to the sea-shore. Periwinkle. 
Syn.—Bacalia, Gray. Isonema, Hall (in part). 
Distr.—175 sp. L. littorea, Linn. (1xix,19). The periwinkles 
are found on the sea-shore in all parts of the world. In the 
Baltic they live within the influence of fresh water, and fre- 
quently become distorted in consequence; similar monstrosities 
are found fossil in the Norwich crag of England. 
Fossil. Rather numerous; Miocene—. Probably some of 
the older fossils referred to Turbo, etc., belong to this genus. 
Shell turbinated, thick, pointed, few-whorled ; aperture rounded, 
outer lip acute, columella rather flattened, imperforate. Oper- 
culum paucispiral, lingual teeth hooked and trilobed; uncini 
hooked and dentated. 
