ARCIDAE 345 



2/4 to 5 inches in length, elongate. Ribs 30 to 38 in number, square, 

 faintly divided by a fine-cut line. Fine, raised, concentric lines seen between 

 weakly beaded ribs. Left valve very slightly larger than right valve. Peri- 

 ostracum light- to dark-brown. Not very common. 



Typical lienosa Say is fossil and very close in characters to floridana. 

 This species has often been called A. secticostata Reeve which is not so 

 elongate and whose origin is unknown. 



Anadara baiighvimii Hertlein Baughman's Ark 



Off the Texas Coast. 



1% inches in length, similar to A. lienosa fioridmia, but much fatter, 

 with 28 to 30 weakly noduled ribs which are not split, and with a strongly 

 posterior-sloping anterior ventral margin. Common offshore down to 50 

 fathoms. A. springeri Rehder and Abbott, published a month later, is this 

 species. 



Anadara transversa Say Transverse Ark 



Plate 27s 



South of Cape Cod to Florida and Texas. 



% to 1/4 inches in lengtli. Left valve overlaps right valve. Ligament 

 fairly long, moderately narrow, rough or pustulose. Ribs on left valve usually 

 beaded, rarely so on right valve; 30 to 35 ribs per valve. Periostracum gray- 

 ish brown, usually wears off except along base of valves. Fairly common in 

 mud below low water. The smallest of the Atlantic Anadaras. Distinguished 

 from ovalis by its longer, wider, more distinct external ligament. A. sulcosa 

 van Hyning 1 946 is this species. 



Subgenus Lunar ca Grav 1847 



The subgenera Argina Gray and Arginarca McLean 1951 are probably 

 the same. 



Anadara ovalis Bruguiere Blood Ark 



Plate 27t 



Cape Cod to the West Indies and the Gulf States. 



1/4 to 2% inches in length, not very thick, roundish to ovate; square, 

 smooth ribs; ligament very narrow and depressed; beaks close together. Peri- 

 ostracum black-brown, hairy. Ribs 26 to 35 in number. 



Dall considered the forms ''pexata Say" and ''americana Wood" too in- 

 distinct for recognition. This species was known for a long time as cam- 

 pechiensis Gmelin and is common. 



