CYPRINID^E. 297 



of W. Wood (C. serratum, Turton), and C. Groenlandi- 

 cum of Chemnitz (C. edentulum, Montagu, and Mactra 

 radiata, Donovan) are not British, although they have 

 been wrongly introduced into our fauna. The first 

 three are tropical, and the last arctic. Dr. Fleming 

 was mistaken in regarding the C. nodosum of Turton as 

 the young of C. muricatum. 



Family XII. CYPRrNID^E, Geinitz. 



Body globose or suborbicular : mantle open in front : tubes 

 sessile or short : gills nearly equal in size : foot tongue-shaped, 

 and adapted for burrowing in sand or mud. 



Shell equivalve, globose or rounded, with a triangular out- 

 line, more or less equilateral, solid, concentrically striated or 

 furrowed : beaks twisted spirally or turned to one side : liga- 

 ment mostly external : hinge short but strong, furnished with 

 two or three cardinal teeth, besides laterals, in each valve : 

 pallial scar entire : muscular scars oval and usually very dis- 

 tinct. 



This family holds a middle rank between the Car- 

 diidce and Venerida, but is more nearly allied to the 

 latter. It differs from Cardiidce principally in the shell 

 not having the longitudinal ribs which characterize that 

 family, and from Veneridce in the tubes of the animal 

 being sessile or short, and in the pallial scar being con- 

 sequently entire at the posterior side. I am not quite 

 satisfied, however, that it is a " good " family, except as 

 regards the single genus Isocardia. 



All the Cyprinidcs are inhabitants of sandy and muddy 

 tracts of the sea-bed. They may, on the whole, be re- 

 garded as northern forms. 



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