344 American Seashelh 



Small byssal gape present on the ventral margin. Moderately common. Area 

 balesi Pilsbry and McLean is this species. 



Genus Arcopsis von Koenen 1885 



Ligament limited to a very small, triangular, or bar-like area bet^veen 

 the umbones. 



Arcopsis adamsi E. A. Smith Adams' Miniature Ark 



Figure 26b 



Cape Hatteras, North Carolina, to Brazil. 



/4 to % inch in length, oblong in shape, moderately fat, flattened sides; 

 white to cream in color. Periostracum very thin. Sculpture cancellate. Lig- 

 ament limited to a very small, triangular, black patch between the umbones. 

 The muscle scars are usually bordered by a calcareous ridge. Inner margin 

 of valves smooth. Common under rocks. 



Subfamily ANADARINAE 



Genus Anadara Gray 1847 



Subgenus Larkinia Reinhart 1935 



Anadara multicostata Sowerby Many-ribbed Ark 



Newport Bay, California, to Panama. 



Shell large, 3 to 4 inches in length, very thick and squarish, 31 to 36 

 radial ribs. The left valve slightly overlaps the right valve. Found in sandy 

 areas by dredging in depths over 12 feet. A. grandis Broderip and Sowerby 

 in Mexican and Panamic waters is larger, heavier and has 25 to 27 ribs. 



Anadara notabilis Roding Eared Ark 



Plate 27P 



Northern Florida to the Caribbean and Brazil. Bermuda. 



1/4 to 3^ inches in length. 25 to 27 ribs per valve. Fine concentric 

 threads cross the ribs and are prominent between the ribs. The ribs never 

 split. Rare in Florida; common in the West Indies. 



Formerly called auriculata Lamarck which is from the Red Sea. A. 

 deshayesi Hanley is a synonym of notabilis. 



Anadara lienosa fioridana Conrad Cut-ribbed Ark 



Plate 27-0 



North Carolina, Florida to Texas and the Greater Antilles. 



