Semelidae 85 



equilateral, longest and a little oblique anteriorly; small, approximate 

 umbos; margins rounded; concentric sculpture of fine, close, equi- 

 distant, elevated threads, more delicate over umbonal region, stronger 

 toward margin, with some intercalated riblets which do not extend to 

 posterior margin; interior polished; anterior muscular impression 

 mitten-shaped; posterior round; pallial sinus deep, rounded, the 

 tip five-tenths millimeter from anterior adductor scar; margins 

 smooth. 



Dredged at six to seven fathoms. 



Genus ABRA (Leach MS.) Lamarck 

 Abra aequalis"^ (gay) Pl. 17, fig. 106 



Alt., 10; length, 12.5; diam., 4.5 mm. Shell small, smooth, white, 

 polished, with thin epidermis; orbicular, well rounded, slightly obli- 

 que; umbos small, pointed, approximate; numerous minute con- 

 centric striations near margins but absent from umbonal area; two 

 small cardinal teeth in right valve, one developed and one vestigial 

 tooth; left valve has remote groove instead of lateral teeth. 



Incredible numbers of this mollusk are sometimes washed upon 

 the Gulf beaches after a prolonged northwest blow. Dredged in two 

 to six fathoms. 



Abra lioicai^e (Dall) PI. 44, fig. 308 



Alt., 6.5; length, 8; diam., 3.5 mm. Shell small, fragile, opaque- 

 white, polished, extremely thin epidermis; umbos small, definite, 

 nearest posterior margin which deviates slightly to the right; sculp- 

 ture solely of concentric growth lines which are accompanied by a 

 different degree of transparency in the shell; teeth as in ^. aequalis. 



Abra lioica is proportionately longer and more oblique than A. 

 aequalis and lacks the groove on the right anterior dorsal margin 

 which is present in A. aequalis. 



Dredged in three to six fathoms. 



Genus CUMINGIAi*' Sowerby, 1833 

 Cnmingia tellinoides (Conrad) PI. 17, fig. 107 



Alt., 10; length, 12; diam., 5 mm. Shell thin, white, long-oval, 



1*^ Span., abra, a bay; Lat., aequalis, even. 

 ^■*^ Gr., leios, smooth. _ 



1*^ Dedicated to the naturalist, Hugh Cunning, who discovered Conus gloria- 

 marts. 



