MARINE MOLLUSKS — MACGINITIE 151 



N. minuta that I examined; however, these differences come well 

 within the normal limits of variation in this species. 



Distribution: Point Barrow, Alaska, south to San Diego, Calif., 

 also to Japan. Madsen (1949) gives the Atlantic range as northeast 

 America south to the Bay of Fundj^; Greenland, Iceland, Spitzbergen, 

 and along Norway and south to the English Channel. 



Nuculana radiata (Krause, 1885) 



Plate 18, figure 2 



Leda pernula var. radiata Krause, 1885a, p. 23, pi. 3, figs. 2a-c. 

 Leda radiata Dall, 1921, p. 11. 



A single live specimen, measuring 23.2 by 12.8 by 7 mm., was 

 dredged at a denth of 80 feet on Aug. 21, 1948. 



Other material examined: None. 



Discussion: Although this specimen appeared to agree with the 

 description and figures by Ki-ause, I am indebted to W. K. Ockelmann 

 for confirming the identification. 



This species has high and prominent umbos, fewer hinge teeth than 

 the smaller A^. minuta, and a periostracum characterized by fine, dark, 

 often broken, radiating ridges that cross the concentric ribs. Soot- 

 Ryen (1932) states that no other species of Nuculana exhibits this 

 curious radiating sculpture. 



Distribution: Soot-E.yen (1932) gives the range of this species as 

 follows: Arctic Pacific : Chukchi and Beaufort Seas, Bering Strait and 

 Sea, and the Sea of Okhotsk. Point Barrow represents a new locality. 



Genus Yoldia MoUer, 1842 

 Yoldia arctica (Gray, 1824) 



Plate 18, figuee 8 



Nucula arctica J. Gray, 1824, p. 214. 



Portlandia arctica G. Sars, 1878, p. 37, pi. 4, figs. 7a-b. 



Leda arctica Oldroj^d, 1924, p. 26, pi. 19, figs. 6, 6a. 



Yoldia arctica Gardner, 1916, p. 518. — Morris, 1951, p. 9, pi. 41, fig. 11. 



A single specimen, 13.9 mm. long bj^ 8.7 mm. high by 5.6 mm. in 

 breadth, was taken on Aug. 4, 1948, at a depth of 28 feet. The shell 

 has a yellowish green periostracum, and apparently is either 3.5 or 4.5 

 years old. 



Other material examined: Over 60 specimens from Spitzbergen, 

 Norway, and Arctic Canada (including about 30 specimens, mostly 

 large, from Wellington Channel); 3 specimens from Collinson Point, 

 Alaska; and about 40 specimens, labeled var. lutescens, collected by 

 Captain Belcher from the "Arctic Ocean." 



Discussion: Specimens vary in color from olive green to brown to 

 brownish black. There is also great variation in the degree of obesity 



