190 ISOCARDTID^. 



inent incurved beaks, hinge with two cardinal and one thin or 

 lamellar posterior lateral tooth in each valve ; ligamental groove 

 long, narrow, marginal ; right valve with a strong, grooved pos- 

 terior and one oblique simple anterior cardinal tooth, the latter 

 running from the beak more or less parallel to the lunular 

 margin ; left valve with a single posterior and a thick anterior 

 cardinal tooth strongly prominent above. /. Balinenais, Laube 

 (cxv, 58-60). 



CALLOCARDiA, A. Ad., 1864. Shell cordate and inflated like 

 in Isocardia, posteriorly scarcely flexuous, thin and without 

 epidermis ; hinge of the left valve with two unequal cardinal 

 teeth, the anterior angularly bent on itself in tiie middle with a 

 triangular pit on either side and with four prominent cusps at 

 the margin ; the posterior oblique, curved, narrow, but elongated, 

 and with two indistinct marginal cusps ; no lateral teeth are 

 present ; pallial line simple and muscular impressions semilunar. 

 There is as jet only one (left > valve of this remarkable species, 

 C. guttata, known from the Chinese Seas. The absence of the 

 posterior lateral tooth, as well as the peculiar cuspidation of the 

 two hinge-teeth, distinguish it. 



isocuLiA, M'Coy, 1844. Under the name of I. ventricosa, 

 M'Coy (cxv, 61) figures a very tumid, cordate shell with a few 

 concentric distant constrictions, indicating stages of growth. 

 The shell appears perfect and closed. 



Cypricardia, Lamarck, 1819. 



Syn. — Trapezium, Muhlfeldt, 1811. Libitina, Schum., 181T. 



Distr.—\^ sp. Red Sea, India and Australia ; in crevices of 

 rock and coral. Fossil, 60 sp. Jurassic — ; North America 

 and Europe. G. rostrata, Lam. (cxvi, 68, 69). 



Shell oblong, with an oblique posterior ridge ; umbones 

 anterior, depressed ; ligament external, in deep and narrow 

 grooves; cardinal teeth 2*2, laterals 1 — I in each valve, some- 

 times obscure ; muscular impressions oval (of two elements) ; 

 pallial line simple. 



Animal (of C. solenoides) with mantle-lobes united, cirrated 

 behind ; pedal opening moderate ; foot small, compressed, with a 

 large byssal pore near the heel ; siphons short, conical, unequal, 

 cirrated externally ; orifices fringed ; palpi small ; gills unequal, 

 the outer narrower and shorter, deeply lamellated, united pos- 

 teriorly, the inner prolonged between the palpi. 



APRICARDIA, Gueranger, 1861. Shell elongated, inequilateral ; 

 hinge with one strong, recurved tooth in each valve, the tooth 

 being in the left valve almost directly under the beak and in the 

 right a little posterior to it ; to each tooth corresponds an equally 

 large cavity in the other valve. This peculiar form resembling 



