290 HELICINIDA. 
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. 
Etym.—Named in honor of Baron Ferussac. 
Syn.—Strophostoma, Desh. 
Distr.—Fossil. Miocene; Europe. fF. 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. 
scoLiostomMaA, Braun. Shell turriculated; aperture rounded, 
turned up upon the spire, entire; lip thick, varicose, reflected, 
F. megalostoma, Sandb. (xxvii, 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 
the exclusion of the animal and shutting upon it when withdrawn ; 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. 

Famity 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 Cyclophoride ; 
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 
