290 HELICINIDiE. 



rimate ; aperture subcircular ; peristome simple, thin, margins 

 widely separated ; columella callously appressed, widely dilated. 

 Operculum testaceous, smooth and flat externally, the nucleus 

 obsolete, slightly concave and costate within. 



Animal without tentacles, the eyes immersed in the top of the 

 head. 



Ferussina, Grateloup. 



Etyvi. — Named in honor of Baron Ferussac. 



Syn. — Strophostoma, Desh. 



Distr. — Fossil. Miocene; Evirope. F. tricarinata, Braun 

 (Ixxvii, 36, 27). 



Shell oval-globular, or subturbinate ; aperture turned upwards 

 and applied to the side of the spire, rounded ; peritreme contin- 

 uous ; umbilicus open, frequently bordered by a spiral keel. 



SCOLTOSTOMA, Brauu. Shell turriculated ; aperture rounded, 

 turned up upon the spire, entire ; lip thick, varicose, reflected, 

 F. megalostoma, Sandb. (Ixxvii, 50). 



Thyrophorella, Greef, 1882. 



Distr. — T. Thomensis., Greef. Island of St. Thomas, W. Coast 

 of Africa. 



Shell sinistral, thin, transparent, nearly orbicular, with a slight 

 yellowish epidermis ; umbilicated ; whorls sharply keeled ; aper- 

 ture half-round, with sharp simple margin ; furnished with an 

 operculum, connected or hinged to the shell instead of being a 

 separate growth of the animal — so that the shell is a true terres- 

 trial bivalve ; the operculum being pushed open like a door for 

 tlie exclusion of the animal and shutting upon it when withdrawn ; 

 the lines of sculpture of the shell are also continued without 

 break upon the surface of the operculum. Terrestrial. 



The animal is not described, although the author states that 

 two of the five specimens obtained contained the soft parts. 

 Not figured. 



Family HELICINID^. 



Shell turbinated, subglobose or depressed; columella generally 

 very callous ; aperture semilunar, with a thick, simple lip ; um- 

 bilicus covered by the columellar callus. Operculum suboval or 

 subtriangular, testaceous or corneous, mostly lamellar. 



Lingual teeth with a single central, flanked on each side by 

 three laterals (xii, 43). Head proboscidiform ; tentacles subulate, 

 with the eyes at their outer bases. Foot elongated. 



The tentacles are more slender and produced and the caudal 

 extremity of the foot is more elongate than in the Cyclophoridse ; 

 the operculum, moreover, is formed on an entirely different plan, 

 and the aperture of the shell, instead of being circular, is semi- 

 lunar in outline^ In their habits they are very similar to the 



