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A3GA ^Edmi n. sp. 



Descrinti on .- Shell very small, elongate, moderatelj' inflat- 

 ed, trapezoidal in outline; both extremities of the dorsal siargin 

 angular; asymmetrically rounded anteriorly, trunoated posteriorly; 

 dorsal and ventral margins parallel; the ventral mar-Tin slightly 

 contrasted medially by the short, narrov/ byssal gape; urabones rel- 

 atively high and prominent, inflated, placed at about the anter- 

 ior third of the len'^th; posterior ridge low and inconspicuous; sou 

 sculpture t; pically of many clear-cut, rounded radial ribs, very 

 narrow in the median portion of the shell and widest in the estreme 

 anterior and posterior portions; the ribs may be finely and faint- 

 ly nodulated by numer-us lov;, concentric raised lines; cardinal 

 area very v;ide, v/lth usually a single set of fine ligament grooves 

 that diverge from the umbones at an acute angle; hinge almost as 

 long as the shell, straight; teeth ruiinterrupt ed medially, fine, 

 numerous; inner marjrin of the shell with relatively deep erenulat- 

 ions except in the meriian ventr;?l portion. 



Dimensions .- length, 10 mm.; alt., 5 mm.; semidiam., 2 mm.; 

 length of hinge 7 mm. 



Remarks .- The members of this species- the most abundant 

 of the true Areas- constitute a highly variable group. Although 

 the typical trapezoi-^al outline is never l§st, some soeciiens are 



