NO. 2183. NEW NORTHWEST AMERICAN BIVALVES— BALL. 403 



Station 4471, Bowers Bank, Bering Sea, in 30 fathoms. 

 The pecuhar narrow oblique form is so far unique in the genus. The 

 margins are smooth. 



LIMOPSIS AKUTANICA, new species. 



Shell white, with a golden brown long-haired periostracum, the 

 sui'face concentrically somewhat irregularly sculptured, the ridges 

 crossed by finer, closer, less conspicuous striae; disk ovate, compressed, 

 with inconspicuous beaks, a very small narrow area and a relatively 

 large resilifer; the inner margins are flat; the hinge plate narrow 

 with about 7 posterior and 9 anterior teeth; interior of the disk 

 finely radially striate. Length, 21; height, 18; diameter, 8 mm. 

 Cat. No. 224263, U.S.N.M. 



Station 2842, southeast of Akutan Island, Aleutians, in 72 fathoms. 



PTERIA VIRIDIZONA, new species. 



Shell small, oval, translucent, sea-green, distributed in narrow 

 darker and lighter zones, sculptured with narrow, very elongate, 

 opake, whitish scales, distributed in radiating lines with wider bare 

 spaces between them; right valve smaller and flatter with a sinus for 

 the byssus; left valve larger with the anterior ear compressed but 

 not sinuate ; the hinge line shorter than the shell with a shallow 

 rounded sinus between the posterior ear and the body of the disk; 

 interior with the pearly area small and no denticulations on the hinge 

 hue. Length, 25; height, 13; diameter, 5 mm. Cat. No. 172600, 

 U.S.N.M. 



Long Beach, California (H. N. Lowe). 



VULSELLA PACIFICA, new species. 



Shell small, irregular, dark purple margined with white, the sur- 

 face sculptured with obscure concentric ridges crossed by fine vermic- 

 ulate radial striations; interior dark purple with white valve 

 margins; resihfer very large and strong, inner valve margins smooth. 

 Length, 9; height, 11; diameter, about 6 mm. Cat. No. 101935, 

 U.S.N.M. 



Nicaragua (Thomas Bridges). 



The specimen may be young, but it seemed worthy of description, 

 since no species of this genus has hitherto been reported from the 

 Americas. 



PSEUDAMUSIUM INCONGRUUM, new species. 



Shell small, white, suborbicular, left valve rather flat with short 

 straight hinge line, ears concentrically scaly, sculpture of disk con- 

 centric continuous low sharp lamellae, crossed by slightly raised 

 radial lines, conspicuous only at the intersections which form in the 



