28 PROCEEDINGS OF THE ACADEMY OF [Jan., 



the Chinese origin of S. simplex Adams and Reeve, 1848, to which 

 S. ruhrolineata has also been tentatively referred. 

 Abra pacifica n. sp. 



Guaymas, Mexico. (Coll. U. S. N. Mus., No. 23,700.) 

 Shell small, thin, white, finely concentrically sculptured, giving 

 the surface a silky look; the concentric lines slightly prominent on 

 the dorsal part of the posterior end; beaks not prominent, slightly 

 anterior, outline elongate, attenuated and pointed behind, rounded 

 in front; with only faint traces of microscopic radial strise or none; 

 hinge normal, right cardinal tooth bifid, anterior right lateral stout, 

 very short, posterior feeble, longer; left valve with a bifid cardinal 

 and no laterals; pallial sinus obscure. Length 9, height 5.5, diameter 

 3.0 mm. 



This is the first species of the genus reported from the Pacific 

 Coast. It was collected by Dr. Edward Palmer. 

 Abra tepocana n. sp. 



Off Cape Tepoca, Lower California, in 14 fathoms. (U. S. N. Mus., 

 No. 108,552.) 



Shell small, white, equivalve, anterior end longer; surface with 

 a dull silky lustre due to extremely minute concentric striation; 

 beaks rather prominent; dorsal margins descending, anterior end 

 rounded evenly into a gently arcuate base, posterior end narrower, 

 blunt, hardly truncate, slightly bent to the right as in a Macoma; 

 right valve with a conspicuous resilifer, a very small cardinal tooth 

 and the laterals obsolete; left valve with the cardinal hardly per- 

 ceptible and no lateral laminae; pallial sinus large, 5.6 mm. deep, 

 rounded in front. Length 8, height 6, diameter 3.5 mm., the 

 beaks behind the anterior end 5 mm. 



Abra palmeri n. sp. 



Ballenas Lagoon on the west coast of Lower California; the 

 Gulf of California (Dr. E. Palmer) ; and Panama Baj^ in 26 fathoms 

 (U. S. N. Mus.). Type locality, Panama Bay. (U. S. N. Mus., 

 No. 96,301.) 



Shell short, high, inflated, white, with a silky surface, and a very 

 thin, polished, pale yellow periostracum ; anterior end and base 

 rounded; beaks subcentral, dorsal margins descending, posterior 

 end attenuated and with the extremity rounded; right valve with a 

 deeply bifid (or double) cardinal tooth, the laterals obsolete; left 

 valve with a single cardinal and no laterals. Length 10, height 8, 

 diameter 5.5 mm. The pallial sinus rounded, 6 mm. deep. 



This species is nearest to A. lioica Dall, of the Atlantic Coast of 

 the United States. 



