346 American Se ash ells 



Subgenus Cunearca Dall 1898 

 Anadara brasiliana Lamarck Incongruous Ark 



Plate 27y 



North Carolina to West Florida to Texas and the West Indies. 



I to 1V2 inches in length; almost as high as long. Beaks facing each 

 other at center of short, transversely striate ligamental area. Left valve over- 

 laps right valve considerably. Ribs 26 to 28, square with strong bar-like beads. 

 Periostracum thin, light-brown. A. mcongnia Say is this species. 



A. chemnitzi Philippi from the Greater Antilles to Brazil is similar, but 

 thick-shelled, less than i inch in length; the beaks are slightly forward of the 

 center of the ligamental area. 



Subfamily NOETllNAE 

 Genus Noetia Gray 1857 



Beaks point posteriorly; valves the same size; ligament transversely stri- 

 ate; posterior muscle scar raised to form a weak flange. 



Subgenus Eontia MacNeil 1938 



The subgenus Eontia is an Atlantic group only. Noetia s. str. differs in 

 having decidedly more regular sculpture, the ribs smoother and never di- 

 vided; deeper and longer crenulations on the inner margin. There is only 

 one Recent American true Noetia (reversa H. and A. Adams) which occurs 

 from the Gulf of California to Peru. 



Noetia ponderosa Say Ponderous Ark 



Plate 27Z; figure 28a 



Virginia to Key West, Louisiana and the Gulf of Mexico. 



2 to 2 % inches in length, almost as high as long. Ribs raised, square and 

 split down the center by a fine incised line; 27 to 31 ribs per valve. Posterior 

 muscle scar raised to form a weak flange. Periostracum thick, black, but 

 wears off at the beaks. A common shallow-water sand-dweller. Fossil speci- 

 mens are rarely found on Nantucket, Massachusetts, beaches. 



Family LIMOPSIDAE 

 Genus Limopsis Sasso 1827 



Rather small, obliquely oval, clams with tufted, velvety brown peri- 

 ostracum. Hinge line curved, with a series of oblique teeth. The hinge 

 resembles that of the Glycymeridae. Ligament external, small, central, tri- 



