367 



quadrata, valva superiore depresso-conica, vertice subcentrali, m 

 feriore planulata extus adha;rente ; cardine et ligamento cardinali 

 nullis. 



Shell of two unequal valves which are equilateral, and of a 

 rounded subquadrate form, though rather irregular on account of 

 its being fixed to rocks, stones, shells, corals, &c. ; upper valve of 

 a flattened conical form, with the vertex near the centre ; lower 

 valve flattened, adhering by its external surface. Hinge and car- 

 dinal ligament none. Muscular impressions in each valve four, of 

 which in the attached valve two are near the centre and approxi- 

 mated (sometimes united), and two are near the posterior margin 

 and distant. In some species there is a prominence just behind 

 the central pair which bears a slight resemblance to a nose, so the 

 shell resembles a front face, whence its name, the posterior mus- 

 cular impressions being compared to eyes, and the two anterior, 

 when united, resembling the mouth. 



Crania is distinguished from Orbicula by its mode of attach- 

 ment; and from Hipponyx by its muscular impressions. These 

 are the only three genera known which are destitute of hinge, and 

 hinge ligament. 



Crania personata (pi. lxxiii. f. 9.) Lam. Hceninghaus motiogr. 



Testse valva inferiore ovato-orbiculari, postice retusa ; cicatri- 

 cibus posterioribus obliquis subreniformibus, anterioribus in unam 

 orbicularem confluentibus, tuberculosis ; rostello nullo, disco pal- 

 mato-radiato, limbo antice incrassato, granuloso. 



Lower attached valve of a rounded ovate form, truncated poste- 

 riorly ; the posterior muscular impressions are somewhat reniform 

 and the anterior are united together forming one orbicular tuber- 

 culated impression, without any rostellum; disk with a radiated 

 palmate impression ; anterior margin thickened, granular. 



India; Eetz, Hoeninghaus. 



We have never met with this species, and have therefore copied 

 the description from Hoeninghaus' Beitrag zur Monographic der 

 Gattung Crania (1828) ; and have to acknowledge our obligation 

 to that gentleman for the drawing which he was so kind as to 

 communicate. 



2. Crania ringens (pi. lxxiii. f. 10, 11.) Hoening. I. c. p. 3. 

 /. 2. a, b. 



Testae valva inferiore suborbiculari, postice retusa, impressi- 



2 g 2 



