192 CARDIID^. 



other transverse to the anterior border) ; posterior scar subcir- 

 cular, superficial ; pallial line faint, entire. 



CLOTHO, Faujas, 1808. Shell oval,subequilateral ; two diverging 

 cardinal teeth in each valve. A. Faujasii (cxv, 65). Tertiary ; 

 Europe. 



Cypricardinia, Hall, 1859. 



Distr. — Silurian, Devonian; JSTew York. C lamellosa, Hall 

 (cxxi,32). 



Shell elongately trapezoidal, moderately compressed, beaks 

 antei'ior or subanterior, slightly prominent, surface concentric- 

 ally lamellated or striated, with a posterior more or less dis- 

 tinct dorsal ridge; the ligament appears to have been thin; 

 muscular impressions ovate, slightly impressed ; hinge unknown. 



This is a rather unsatisfactoril}'^ known palaeozoic genus ; the 

 shells have the aspect of Cypricardia, but appear to be thinner, 

 and nothing is known of their hinge by which their proper clas- 

 sification could be decided. 



Family CARDIIDJE. 



Shell regular, equivalve, free, cordate, ornamented with 

 radiating ribs ; posterior slope sculptured differently from the 

 front and sides; cardinal teeth two, laterals 1-1 in each valve.; 

 ligament external, short and prominent ; pallial line simple or 

 slightly sinuated behind ; muscular impressions subquadrate. 



Animal with mantle open in front ; siphons usually very short, 

 cirrated externally ; gills two on each side, thick, united poste- 

 riorly ; palpi narrow and pointed ; foot large, sickle-shaped. 



Cardium, L., 1758. 



Etym. — Kardia, the heart. Cockle. 



Distr. — 100 sp. World-wide; from seashore to 140 fathoms. 

 Grregarious on sands and sandy mud. Fossil, 330 sp. Upper 

 Silurian — . 



Shell ventricose, close or gaping posteriorly; umbones promi- 

 nent, subcentral ; radiately ribbed; margins crenulated ; pallial 

 line more or less sinuated. 



Animal with the mantle-margins plaited ; siphons clothed 

 with tentacular filaments, anal orifice with a tubular valve ; 

 branchial fringed; foot long, cylindrical, sickle-shaped, heeled. 



The cockle (G. edule) frequents sandy bays, near low-water; 

 a small variety lives in the brackish waters of the river Thames, 

 as high as Gravesend, England ; it ranges to the Baltic, and is 

 found in the Black Sea and Caspian. G. rusticum extends from 

 the Icy Sea to the Mediterranean, Black Sea, Caspian and Aral. 

 On the coast of Devon (England) the large prickly cockle (G. 

 aculeatum) is eaten. 



