MARINE MOLLUSKS — MACGINITIE 187 



occupied. Jensen (1901) also recognized that the northern form of 

 Mya commonly assigned to M. arenaria is not this species, and he gave 

 to this northern European form the name of M. truncata forma ovata. 

 Madsen (1949), who found no M. arenaria in an extensive collection 

 from Iceland, also uses the name ovata as a form of M. truncata, but 

 Foster (1946) and Soot-Ryen (1951) consider M. truncata forma ovata 

 Jensen a synonym of M. pseudoarenaria Schlesch. 



Schlesch (1931) considered this northern form sufficiently distinct 

 to warrant a specific name, as it probably does. Although he does not 

 mention M. japonica Jay (1856),'^ he does refer to AI. intermedia Dall, 

 statmg that he considers the latter distinct from M. pseudoarenaria. 

 He states (translated from German): "It is astonishing, however, that 

 M. intermedia Dall, also with M. arenaria, extends to Monterey in 

 California. It shows therein greater agreement with M. arenaria than 

 with M. truncata, which only extends to Puget Sound. While M. 

 pseudoarenaria goes heart in hand with M. truncata, M. intermedia 

 obviously stands closer to M. arenaria, a phenomenon of convergence." 

 Although M. japonica Jay (^Dall's M. intermedia) is undoubtedly 

 closely related to M. arenaria, and M. pseudoarenaria is more closely 

 related to M. truncata, Schlesch's idea of convergence as related to 

 range was based on Dall's misidentification of several small shells 

 from the vicinity of Monterey. The specimen from Monterey Bay 

 (in the U. S. National Museum) is not even a Mya; the 3 small speci- 

 mens (about one-quarter inch long) from San Francisco Bay are 

 undoubtedly the young of M. arenaria; and the 2 specimens (also meas- 

 uring about one-quarter inch) from 13 fathoms off Punta Afio Nuevo, 

 Calif., are almost certainly the young of M. arenaria. But a specimen 

 (about one-half inch long) from the Gulf of Georgia, British Columbia, 

 and another specimen (about 1% inches long) from Bellingham, 

 Wash., appear to be the young of M. pseudoarenaria. 



DaU's lectotype of M. intermedia is shown in plate 19, figure 6. 

 Since the name intermedia is unavailable, the figured shell can un- 

 doubtedly be assigned to M. japonica Jay. Jay (1856, p. 292) states 

 that M. japonica "is similar to M. arenaria, but differs in the pallial 

 impressions, which are much more profound, the tooth more thickened, 

 a deep notch on its posterior, and an elevation on the anterior side, 

 and the whole shell more ponderous and incrassated." In the speci- 

 men figured by Jay (1856, pi. 1, fig. 10) the palhal sinus is not so deep 

 and the anterior end is not so long and high as in Dall's lectotype, in 

 which the sinus is imusually large. In many specimens of M. japonica 

 the pallial sinus is no deeper than in most M. arenaria (cf. pi. 19, fig. 



'8 The date for Mya japonica Jay is usually given as 1857, but M. O. Perry's account, containing Jay's 

 report on the shells, was published In 1856. Two editions of Perry's narrative, a quarto and an octavo, 

 were published, both in 1856. 



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