CARDIACEA. MOLLUSCA. CARDITA. 93 



slightly forwards, nearly central ; anterior margin regularly round- 

 ed ; posterior side somewhat elongated, margin protuberant below 

 the ligament, bordered by a slight wave, which gives the posterior 

 termination a somewhat sinuous or truncated appearance, and 

 leaves the shell gaping at this point; this region is also more 

 coarsely wrinkled than the rest ; surface marked with minute lines 

 of growth, divided into zones by darker indications of the stages 

 of growth, which successive increments appear very loosely at- 

 tached posteriorly ; these are crossed by numerous, inconspicu- 

 ous, radiating ridges ; epidermis thin, shining, of a drab or very 

 light fawn-color ; hinge slender ; cardinal teeth nearly wanting ; 

 lateral teeth distinct, but small ; muscular and palleal impressions 

 profound, within which the shell is opalescent-white, the margin 

 light salmon-color ; edge slightly crenated. Length 2| inches, 

 height 2/^ inches, breadth 1| inch. 



Brought from the Grand Banks, but not as yet found on the 

 shores of this State. 



This singular shell, from its triangular, compressed form, and its 

 smooth surface, has rather the aspect of a Mactra than a Cardium. 

 The not unfrequent entire want of cardinal teeth, has misled one dis- 

 tinguished conchologist as to its true relations, while its external char- 

 acters have so little point, that another was not led to it by any exist- 

 ing description, and made of it a new species. Dr. Loven informs me, 

 that Beck has instituted a new genus for it which he calls Serripbs, 

 on account of the serrated margin of the foot. 



The old shells, one of which measures in height 3^ inches, in 

 length 3^1 inches, in breadth l^ inch, become solid and strong, and also 

 more tumid, especially behind. The young shells often have the sur- 

 face variegated with stripes, or angular markings, of rusty-brown color. 

 This species is also remarkable for gaping posteriorly to a considera- 

 ble extent. 



Genus CARdItA, Lam. 



Shell inequilateral^ regular^ hinge with a short, strong, erect 

 tooth under the beaks, and an oblique one stretching along the 

 margin. 



