48 Lamai'ck's Genera of Shells. 



Type. Radiolites rotulans *. 

 Valves of the shell conical, applied base to base, rather 

 short, subequal. Pyrenees. PI. II. Fig. 99. 



3. Calceolat. 



Shell inequivalve, triangular, turbinated, flattened below. 

 Largest valve hood-shaped, obliquely truncated at the aperture : 

 cardinal margin straight, transverse, slightly notched, and in- 

 dented in the middle ; superior margin arched. Smaller valve 

 flattened, semi-orbicular, opercular, with a tubercle on each 

 side of the cardinal margin, and in the middle a pit with a 

 small lamina. 



The calceola is a thick, solid shell, and in form not unlike a 

 half-sandal. Its cavity is striated from the centre to the cir- 

 cumference. The upper (flat) valve is marked externally with 

 concentric strife ; its cardinal margin seems to articulate with 

 the turbinated valve by a straight, linear, transverse hinge. In 

 some individuals, the upper valve is slightly convex. Its lateral 

 tubercles have three grooves. 



One species. Calceola sandalina. X- ('Anomia sandalium, im?;.) 



No further description. Environs of Juliers. PI. II. Fig. 100. 



4. Birostrites §. 



Shell inequivalve, bicornute ; valves, in consequence of the 

 elevation of the disc, conical, unequal, obliquely diverging, 

 nearly straight, hornshaped ; the base of one valve enveloping 

 that of the other. 



The birostrites is composed of two pieces, or valves, not 

 united by the margins of their bases, but one valve enveloping the 

 other, and the dorsal disc of each elevated into an almost 

 straight cone, slightly arched within. These hornshaped valves, 

 are unequal, and diverge obliquely in the form of a very open V. 

 One valve appears to spring from the base of the other, the 

 shorter being always the enveloped valve. The interior of the 

 shell is unknown. 



One species. Birostrites inequiloba \\. 



* From rotula, a littk wheel. t Cakeolus, a little shoe, 



t From sandalum, a sandal. 



^ From bis, twice, or double, and rostrum, a beati. || Unequally lobed. 



