CERITHIID^. 249 



Mesostoma, Deshayes, 1864. 



Distr. — Fossil, 4 sp. Eocene ; Paris. M. grata^ Dh. 



Shell elongated, turreted, scalariform ; aperture nearly circu- 

 lar, dilated, obliquely cut, terminating in front by a semicanal- 

 iculated angle; columella slightly concave, cylindrical, obliquely' 

 truncated, lip simple, and slightly expanded. 



ExELissA, Piette, 1861. 



Etym. — Uxelisso, to unfold. Syn. — Kilvertia, Lycett, 1863. 



Distr. — Fossil, 14 sp. Mid. Lias to Kimmeridge Clay; 

 England and France. Cretaceous, 1 sp. (?) ; India. E. formosa^ 

 Lycett (Ixix, 62). 



Shell small, elongated subcylindrical, somewhat pupiform, 

 many-whorled, perpendicularly costated, tuberculated or spined ; 

 last whorl cylindrical, contracted at the base, with a tendency 

 to separate from the axis ; aperture orbicular, entire, the lips 

 elevated, produced, and slightly thickened ; columella solid. 



Includes a large number of very characteristic transversely 

 ribbed species. It is uncertain whether there was an anterior 

 canal or not, and therefore the ]3ertinence of the genus to this 

 family remains doubtful. 



Fastigiella, Reeve* 



Distr. — 1 recent sp. ; and an Eocene sp., Paris basin. F. 

 carinata, Reeve (Ixx, 64). 



Shell elongated, turriculated, whorls rounded, with revolving 

 ribs ; aperture prolonged into a short, slightly twisted canal ; 

 axis rimate. 



Triforis, Deshayes. 



Syn. — Tristoma, Blainv. 



Distr. — 100 sp. E. Indies, Polynesia, Australia, Panama, W. 

 Indies, Mediterranean. Fossil. Eocene; Europe. T.perversus^ 

 Linn. (Ixix, 58). 



Shell sinistral, sculptured, granular; whorls numerous, termi- 

 nating below in a small aperture, with tubular anterior canal ; 

 opposite this canal is sometimes a second one upon a varix, 

 marking the position of a former aperture. Operculum orbicu- 

 lar, few-whorled. 



Animal. Tentacles clavate at the tips, united at their bases 

 by a sinuated veil. 



INO, Hinds. (Inella, Bayle.) Shell cylindrically subulate, 

 elongated, spire sharp-pointed. T. corrugatus^ Hinds (Ixix, 59). 



SYCHAR, Hinds. Shell elongated, whorls rounded. T. vitreus, 

 Hinds (Ixix, 60). 



MASTONiA, Hinds. Shell acuminated, swollen in the middle. 

 T. vulpinus, Hinds (Ixix, 61). 



L^ococHLis, Dunker and Metzger. Shell turreted ; whorls 

 17 



