180 CONCHYLIA— jDirHyi?^. 41. 



This genus forms a very natural family, distinguished by the 

 heart-shaped form, the longitudinal ribs which are in general strong- 

 ly marked and prominent, and by the four teeth in each valve, two 

 of them close together and a little oblique, and a remote lateral one 

 on each side in each valve, all locking together. In some of them 

 one of the cardinal teeth in one of the valves is minute and nearly 

 obliterated ; and some have an oblique rib-like denticle in addition 

 to the lateral tooth on the hinder side in the right valve, as if this 

 tooth were doubled. 



They are in general inhabitants of sandy coasts, where they lie 

 imbedded at no great distance from the shores, and are easily rooted 

 up by any violence of surf. 



* Valvis spinosis aut tuberculatis. 1-6. 

 The ribs armed with spines or tubercles. 



acuieatum. Caedium testd tumidd tenui obliqua, anticS subangulatd, costis 21, 

 anticis spinosis posticis papillosis, sulcis transversim striatis. 

 Shell tumid thin and oblique, a little angular on the anterior side, 

 with 21 ribs, the anterior ones of which are spinous and the hin- 

 der ones warty, the interstices striate transversely. 

 Tab. nost. 13, fig. 6, 7. 

 Cardium aculeatum. Linn. Syst. Nat. p. 1 122. 

 Gmelin, Syst. p. 3247. 

 Turton, Linn. Syst. iv. p. 201. 

 Pennant, iv. p. 187, tab. 53, fig. 1. 

 Da Costa, Brit. Conch, p. 175. 

 Donovan, British Shells, i. tab. 6. 



