172 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vol. 50 



Genus MODIOLARIA Beck 

 MODIOLARIA IMPRESSA Dall, n. sp. 



Shell small, thin, arcuate, elongate, olive-green or brownish, with 

 a small striate anterior area, deeply impressed middle area, and 

 large, tumid, nearly smooth posterior area ; surface polished, beaks 

 very anterior, inconspicuous ; anterior area very short, with about 

 six pairs of strong radial r'iblets ; middle area polished, smooth, gap- 

 ing below for the byssus, where the margin is a little convex, behind 

 which it is conspicuously excavated ; posterior area swollen, arcuate 

 above, produced behind and below, dropping vertically to meet the 

 depressed middle area, faintly concentrically and obsoletely minutely 

 radially striated ; interior pearly ; inner margins crenulate around 

 the distal areas, medially smooth, with a few interlocking denticula- 

 tions just behind the internal ligament, but none in front of the 

 beaks ; byssus strong. Alt., 10 ; Ion., 19 ; maximum diameter, 9 mm. 



U. S. S. Albatross, station 4677, June 5, 1906, in 52 fathoms, 

 Bering Sea. U. S. Nat. Mus., 110,467. 



Peculiar on account of the strong constriction of the middle areas 

 and the arcuate form. 



Genus LIOCYMA Dall 

 LIOCYMA ANIWANA Dall, n. sp. 



Shell small, solid, pale grayish or straw-color, with low, rather 

 anterior beaks ; anterior end short, rounded ; posterior end longer, 

 attenuated ; base evenly arcuate ; about two-thirds of the valve with 

 strong concentric waves with subequal interspaces, the remainder 

 concentrically striated ; interior bluish white, with the middle of 

 the disk yellowish ; pallial sinus very short ; hinge normal, heavy. 

 Lon. of shell, 24; alt., 18; diameter, 13 mm. Vertical of the beaks 

 about seven mm. behind the anterior end ; the beaks somewhat 

 eroded. 



Station 5013, in 43 fathoms, Aniwa Bay, at the south end of 

 Sakhalin Island. U. S. Nat. Mus., 110,511. 



Ruder, more inflated and solid, and more attenuated behind than 

 any of the arctic or Aleutian species. 



Genus PHOLADOMYA Sowerby 

 PHOLADOMYA PACIFICA Dall, n. sp. 



Shell thin, whitish, more or less minutely granular on the exterior 

 surface, with a very thin pale yellowish periostracum, equivalve, 

 nearly equilateral; form resembling that of Mya arenaria, but pro- 



