DRANIID^-. 5S3 



Species of Rhynehonella. 



Grayi, Woodw. psittacea, Chem. 



nigricans, Sow. 



Fam. CKANIID.E. 



Animal with its oral arms fixed to a process of the lower 

 or ventral valve. 



Shell calcareous, minutely tubular, attached to marine 

 bodies by the outer surface of the ventral valve which is 

 imperforate ; upper or dorsal valve simple, conical. Hinge 

 and apophysary system wanting. 



This family differs from Discinidce in the calcareous 

 structure of the shell and in the ventral valve being entire 

 and attached by its outer surface. The position of the ani- 

 mal on its ventral side is, however, the same as in that 

 family. 



Genus CRANIA, Retzius. 



Shell calcareous, tubular, without hinge or internal cal- 

 careous appendages; ventral or fixed valve not perforated 

 for the passage of a peduncle of attachment, the interior 

 with a central process to which the fleshy spiral arms are at- 

 tached; dorsal or upper valve free, limpet-like, with two 

 diverging muscular processes. 



Syn. Criopus, Criopoderma, Poll. Cryopus, Desk. Cra- 

 niolithes, Schloth. Orbicula, Cuv. Discina, Turt., not 

 Lam. 



Ex. C. anomala, Midler, pi. 132, fig. 3. Shell, C.ano- 

 mala, fig. 3, a, 3, b. 



The species of Crania inhabit deep water, and are found 

 in India, New South Wales, the Mediterranean, Britain, 

 and Spitzbergen. 



