472 MANtJAI 01* THE MOLLTTSCA. 



Sub-genus. FewencarcZm, Lamarck. Y. ajar, PI. XX., Pig. 6. 

 Shell cordate, ventricose ; hinge without lateral teeth. Animal 

 locomotive, with a sickle-shaped foot like the cockles. 



Distribution, 54 species. Chiefly in tropical seas, on rocky- 

 bottoms and in shallow water ; the Venericardice on coarse sand 

 and sandy mud. West Indies, United States, West Africa, 

 Mediterranean, Eed Sea, India, China, Australia, New Zealand, 

 Pacific, West America. C. horealis, Conrad, inhabits the sea of 

 Ochotsk ; 0. ahyssicola, Hinds, ranges to 100 fathoms ; 0. 

 squamosa, to 150 fathoms. 



Fossil, 170 species. Trias — . United States, Patagonia 

 Europe, Southern India. 



? Yebticordia, Searles Wood, 1844. 



Synonyms, Hippagus, PhUippi, not Lea. Trigonulina, B'Orb. 

 [Verticordia, a name of Yenus.) 



Type, Y. cardiiformis (Wood, in Sby. Min, Con.)) 1^1- XYIL, 

 Pig. 26. 



Shell sub-orbicular, with radiating ribs ; beaks sub-spiral ; 

 margins denticulated ; interior brilliantly pearly ; right valye 

 with 1 prominent cardinal tooth ; adductor scars 2, faint ; 

 pallial line simple ; ligament internal, oblique ; epidermis dark 

 brown. 



Distrihution^ 2 species. China Sea (Adams) ; Mediterranean ? 

 (Forbes. '^ 



Fossil, '2 species. Miocene — . Britain, Sicily. 



Hippagus isocardioides. Lea, 1833, Eocene, Alabama, is eden- 

 tulous. Trigonulina ornata, D'Orbigny, Jamaica, has hinge-f 

 teeth 2.2 ; right valve with a long posterior tooth. Epidermis 

 of large nucleated cells, as in Trigoniadce, to which family it 

 undoubtedly belong 



Section h, — Sinu-I'Allialia. 

 Respiratory siphons long ; pallial line- sinuated, 



Pamilt XIY. — Yeneeid^. 



Shell regular, closed, sub-orbicular, or oblong ; ligament 

 external ; hinge with usually 3 diverging teeth in each valve ; 

 muscular impressions oval, polished ; pallial line sinuated. 



Animal free, locomotive, rarely byssiferous or burrowing; 

 mantle with a rather large anterior opening ; siphons unequal, 

 united more or less; foot linguiform, compressed, sometimes 

 grooved ; palpi moderate, triangular, pointed ; branchiae large, 

 sub-quadrate, united posteriorly. 



