MARINE MOLLUSKS — MACGINITIE 171 



Cardita paucicostafa is the young of C. crassidens or a C. crassidens 

 that has been favored by fate. Wlien the latter species does not 

 grow in cramped quarters and does not become eroded and covered 

 with other animals, it shows the same color and texture of periostracum 

 attributed to C. paucicostata, and the length tends to remain equal to 

 the height. 



A shell from Point Barrow that is 24 mm. long by 22 mm. high is 

 about 4 years old, and another 24 mm. long by 20 mm. high is about 

 5 years old. 



Distribution: Point Barrow to Puget Sound. Point Barrow is 

 a new locality. 



Family Thyasiridae 



Genus Thyasira Lamarck, 1818 



Thyasira flexuosa (Montagu, 1803) 



Var. sarsi Philippi 



Plate 4, figure 12 



Tellina flexuosa Montagu, 1803, p. 72. 



Lucina flexuosa Gould, 1841, p. 71, fig. 52. — flexuosa Philippi, 1845a, p. 74. 



Lucina gouldii Philippi, 1845a, p. 75, pi. 2, fig. 7. 



Axinus sarsii Philippi, 1845b, p. 91.— G. Sars, 1878, p. 60, pi. 19, figs. 6a-b. 



Cryptodon gouldii Gould, 1870, p. 100, fig. 406. 



Axinus flexuosus G. Sars, 1878, p. 59, pi. 19, figs. 4a-b. 



Axinus gouldii G. Sars, 1878, p. 60, pi. 19, figs. 6a-b. 



Thyasira gouldii Morris, 1952, p. 36, pi. 8, fig. 15. 



A single living specimen 6.2 mm. long by 6.2 mm. high was dredged 

 through the ice on Feb. 18, 1950, at a depth of 162 feet. 



Other material examined: Numerous specimens of var. gouldi 

 from Norway, Spitzbergen, Iceland, Greenland, Nova Scotia, and 

 Massachusetts; over 50 specimens of var. gouldi from localities ranging 

 from Bering Strait to Juan de Fuca Strait and off Point Loma, Calif. 



Discussion: Madsen (1949) states that it is common practice to 

 regard T. gouldi and T. sarsi as forms of T. flexuosa and Soot-Ryen 

 (1932) treats them as such. T3^pical T. flexuosa and forma gouldi are 

 higher in proportion to the length than forma sarsi. Both T. flexuosa 

 and forma gouldi are somewhat truncate on the anteroventral border, 

 whereas forma sarsi is evenly rounded (pi. 4, fig. 12). However, in 

 a lot of about 30 specimens (Stanford collection) from Maine labeled 

 T. gouldi, there are a few specimens that are evenly rounded antero- 

 ventrally. Madsen (1949) further states that the ''form common in 

 Iceland is the American gouldi," but that a few large specimens have 

 the sarsi form. 



478771—59 8 



