184 AXEL A. OLSSON 



Superfamily CAKDITACEA 



Family Carditidae 



Shell suborbicular to subquadrangular, often cordate, usually heavy, 

 with large, prominent umbones, anteriorly directed and varying in position 

 from submedian to nearly terminal, the anterior side commonly the shorter. 

 Sculpture consists typically of strong, radial ribs, usually noded, the sur- 

 face covered by a brown, hairy periostracum. Ligament external. Hinge 

 plate curved, usually with 2 cardinal teeth in each valve, the posterior one 

 elongate and with the lateral teeth absent or more or less degenerated. 

 Pallial line simple, the ventral margin more or less fluted or crenated by 

 the ends of the radial ribs. Byssus usually present. 



Two genera, roughly distinguished as follows: 



I. Shell rounded, trigonal or cordate, the umbones submedian, a little 

 nearer the anterior side. Lateral teeth absent or vestigial. 



Genus Cardita 



IL Shell elongate to oblong, the umbones placed much nearer the anter- 

 ior end, the posterior side often drawnout and more strongly sculptured. 

 Lateral teeth more strongly developed. 



Genus Carditamera 



Genus CARDITA Bruguiere, 1792 



Type species by subsequent designation. Children, 1823. C. sulcata 

 Bruguiere (=:Chama antiquata Linne). Recent. Mediterranean Sea. 



Shell rounded, trigonal, cordate, solid, usually strongly ribbed, the ribs 

 being generally noded. Umbone swollen, terminating in a coiled prosogyrate 

 beak projecting over a small, deep lunule. Ligament external, the margin 

 slightly overhanging the resiliferal scar. Hinge plate heavy, the right valve 

 with a large, massive, central tooth bordered by sockets on each side; the 

 left valve has two cardinal teeth and a large, wide, central socket, the 

 posterior tooth elongated, the anterior one small, and it is often bordered 

 by a small, vestigial tooth at the base of the lunule. Lateral teeth are 

 lacking or vestigial. The adductor scars are large, subequal, the pallial line 

 entire. Margins of the valves are deeply fluted by the ends of the ribs. 



The hinge pattern of Cardita is characteristic but has received different 

 interpretation by authors. The large, massive, central cardinal tooth of 

 the right valve is diagnostic; the base of this tooth is flattened or excavated 

 and extended backwards along the inner edge of the hinge plate; it fits into 

 a large, central socket in the opposite valve. C. cuvieri has a small, 

 vestigial anterior tooth in the left valve which is received in a small, pit- 

 like socket in the right. A similar tooth is also found in C. tricolor. 



General key to Panamic-Pacific species 



L Shell of average or large size. Lateral teeth absent or obsolete. 



A. Sculpture formed by strong, coarsely noded, elevated ribs separated 



by deeply grooved interspaces, 

 a. Shell relatively coarse and heavy. Posterior-dorsal submargin deeply 



grooved or excavated. 



