210 NATICID^. 



which takes the salmon to the river, and the herring to shallower 

 water, migrated inshore and sought its proper spawning ground. 



MARSENiNA, Gray. (? Colobocephalus, M. Sars.) Shell opaque, 

 with short spire ; animal with mantle fissured down the back. 

 L. depressa^ Sutton (Ixiii, 59). 



ONCHiDiopsis, Bergh. Shell entirely enclosed by the animal, 

 thin, slipper-like, without spire, margin entire. Animal verru- 

 cose, with a lanceolate foot. 0. glacialis^M. Sars (Ixiv, 12, 73;. 

 Norway. 



CRYPTOCELLA, H. and A. Adams. Shell thin, pellucid, calca- 

 reous ; spire small, mouth very large ; animal with depressed, 

 subverrucose or smooth mantle. L. tentaculata, Mont. (Ixiii, 60). 

 L. Zatens, Mull. (Ixiii, 61). 



CORIOCELLA, Blainv. Shell spiral, calcareous, thin, svibopaque, 

 spire short, whorls rounded, the last large, aperture very large. 

 Mantle of animal deeply fissured and bilobed in front, the surface 

 depressed and covered with numerous hexagonal tubercles. 

 This group was founded by Blainville upon an animal accidentally 

 deprived of its shell. L. nigra, Blainv. (Ixiii, 62, 63). 



Yanikoro, Quoy and Gaimard. 



Syn. — Narica, Recluz. Merrya, Gray. Leucotis, Sowb. 



Distr. — 25 sp. West Indies, Nicobar, Philippines, Polynesia. 

 Fossil. Gault — ; Europe, U. S. V. cancellata, Chemn. 

 (Ixv, 90). 



Shell subglobose, external, white, with sometimes a velvety 

 epidermis, striated, costate or decussated, umbilicated, umbilicus 

 without a trace of callus. Operculum ver}' thin, corneous, not 

 spiral. 



Probably most of the Jurassic and triassic species of Neritopsis 

 belong to Yanikoro, as certainly do nearly all the species 

 described by Mlinster and Klipstein from St. Cassian under the 

 name of Naticella. There are numerous cretaceous species from 

 the old world. 



VANiKOROPSis, Meek. Shell subglobose, thick and solid ; body- 

 volution large ; spire depressed ; aperture ovate ; axis imper- 

 forate ; outer lip simple, beveled ; inner lip closely folded upon, 

 and adhering to, the columella and the body-volution, very little 

 thickened and not fiattened, toothed, notched, or serrated ; surface 

 with distinct revolving lines and furrows, and on the body- 

 volution developing strong oblique folds or plications and 

 furrows, parallel to the lines of growth. N. Tuomeyana, M. and 

 H. (Ixiv, 81). Cretaceous; Upper Missouri River. 



NATicoDON, Ryckholt. Shell globose like Yanikoro, but the 

 inner lip usually thickened and always provided with some kind 

 of a tooth ; the columella is either slightly hollowed out or solid ; 

 the surface smooth or ornamented with various spiral or trans- 



