MARINE MOLLUSKS — MACGINITIE 163 



there is more inequality of the valves than in T. myopsis. There is 

 also more of a dip in the anteroclorsal margin in T. curta than in T. 

 myopsis. 



Distribution: Point Barrow south to the Aleutians and Port Etches 

 (about lat. 60.3° N., long. 146.3° W.), also Plover Bay, Siberia. 

 Madsen (1949) gives the Atlantic range of T. myopsis as northeastern 

 America south to Massachusetts; Greenland; Iceland, Norway north 

 of Bergen, and Spitzbergen to the Kara Sea. It is new to the Pacific 

 and the Pacific area of the Arctic. 



Thracia iLampeia)^ new subgenus 



Type species: Thracia adamsi, new species. 



Shell small, inequivalve, ovately-subquadrate, rounded anteriorly, 

 broadly truncate posteriorly, anterior end longer than posterior, right 

 valve higher and more convex than left; ligament external, thin; hinge 

 edentate; resilium large, elongate-trigonal; with a large buttressed 

 resilifer tapering posteriorly beneath the beaks. 



The buttressed resilifer distinguishes this group from others of the 

 family. 



Remarks. — This subgenus probably belongs close to subgenus 

 Thracia (Thracia). It is named in honor of Mr. Chester Lampe, head 

 Eskimo employee at the Arctic Research Laboratory, Point Barrow 

 base, Alaska. 



Thracia adamsi, new species 



Plate 18, figure 9; Plate 21, figuees 7, 8; Plate 24, figure 8 



Shell small, white, inequivalve, right valve higher and deeper than 

 left; covered with a fairly thick brown periostracum ; beaks directed 

 posteriorly; posterior end the shorter, broadly sub truncate, with a 

 faint radial ridge bearing along the lower two thirds a few microscopic 

 spinelets and a suggestion of a second row of spinelets midway of the 

 area posterior to the ridge; anterior end obtusely rounded; ventral 

 margin only slightly convex; periostracum smooth in center and finely 

 wi'inkled near the margins; sculpture of faint concentric lines of growth; 

 ligament external, thin; resilium large, elongate-trigonal; a large, 

 elongate-trigonal resilifer extending in an obliquely posterior direction 

 from the beaks, solidly attached to the shell throughout its length 

 except near its anteroventral margin where it is buttressed by about 

 15 short pillars separated by shallow pits of about the same width as 

 the pillars, and separated from the anterodorsal edge of the shell by a 

 large, deep pit. Interior of shell chalky; posterior adductor muscle 

 scar large, rounded; anterior, large, elongate. Central portion of 

 pallial line somewhat wavy; pallial sinus of medium size, broadly 



