108 CYPEINID^E. 



dead specimen of that species has been taken ; but we have 

 often seen the minute A. triangularis alive. Cyprina and 

 Isocardia by their hinges indicate some alliance with the 

 Cardiada. 



This family has considerable affinities with the Veneridce, 

 but is distinguished by the very short, almost sessile siphons, 

 and the consequent absence of pallial impression so con- 

 spicuous in that group. 



CYPRINA, Lamarck. 



C. ISLANDICA, Linnaeus. 



C. Islandica, Brit. Moll. i. p. 441, pi. 29 ; (animal) pi. M. f. 4. 



Animal suborbicular, thick, bluish- white ; mantle open, 

 powdered for some depth, on a pale yellow ground, with 

 minute red-brown sandy points ; its edge is finely dentated 

 and marked with a slender brown line. The foot is thick at 

 the base, moderately long, linguiform, and posteally lanceolate. 

 The mantle forms no tubes, but mere sessile orifices, both of 

 which are ciliated ; the branchial is the largest, having about 

 twenty simple cirrhi, the anal about ten ; both are tinged with 

 red-brown ; the anal orifice at its terminus frequently pro- 

 trudes a globular transparent membranous valve, which regu- 

 lates the entry and issue of the water ; the margins of both 

 orifices at the base of the cirrhi have a girdle of a narrow 

 bright red line, the hues of which vary in individuals even 

 from the same locality. 



This species usually inhabits the littoral sandy districts, but 

 at Exmouth is obtained in an offing of five or six miles. 



ISOCARDIA, Lamarck. 



I. COR, Linnseus et Auct. 



/. cor, Brit. Moll. i. p. 472, pi. 34. f. 2; (animal) pi. N. f. 6. 



"Animal globular; mantle completely lining the shell, 

 double at the outer edge ; exterior fold divided in front, open 



