472 MANUAL OF THE MOLLUSCA. 
Sub-genus. Venericardia, Lamarck. V. ajar, Pl. XX., Fig. 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, Red Sea, India, China, Australia, New Zealand, 
Pacific, West America. (0. borealis, Conrad, inhabits the sea of 
Ochotsk; C. abyssicola, Hinds, ranges to 100 fathoms; C. 
squamosa, to 150 fathoms. 
Fossil, 170 species. Trias—. United States, Patagonia 
Europe, Southern India. 
? VERTICORDIA, Searles Wood, 1844. 
Synonyms, Hippagus, Philippi, not Lea. Trigonulina, D’Orb. 
(Verticordia, a name of Venus.) 
Type, V. cardiiformis (Wood, in Sby. Min. Con.), Pl. XVII., 
Fig. 26. 
Shell sub-orbicular, with radiating ribs; beaks sub-spiral; 
margins denticulated; interior brilliantly pearly ; right valve 
with 1 prominent cardinal tooth; adductor scars 2, faint; 
pallial line simple; ligament internal, oblique; epidermis dark 
brown. 
Distribution, 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- 
teeth 2.2; right valve with a long posterior tooth. Hpidermis 
of large nucleated cells, as in Trigoniade, to which family it 
undoubtedly belong 
SECTION b.—SINU-PALLIALIA. 
Respiratory siphons long ; pallial line sinuated. 
Famity XIV.—VENERIDA. 
Shell regular, closed, sub-orbicular, or oblong; ligament 
external; hinge with usually 3 diverging teeth in each valve ; 
muscular impressions oyal, 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 ; branchiz large, 
sub-quadrate, united posteriorly. 
