NO. 1 SOOT-RYEN : THE FAMILY MYTILIDAE 81 



Occurrence: Valves have been obtained in depths ranging from 2 to 250 

 fms. As no living specimens are preserved in the Hancock material, the 

 depth ranges of this species cannot be stated. 



Distribution: Records of valves are from Callao, Peru, north to San 

 Miguel Island, California, including the Gulf of California. 



Grenella decussata (Montagu) 1808 



Plate 8, figs. 43, 45 



Mytilus decussatus Montagu, Testacea Britannica, SuppL, 1808, p. 69. 

 Holotype: British Museum. 

 Type loc: Scottish coast. 



Remarks: Whether the Pacific specimens really belong to the Atlantic 

 C. decussata (Montagu) is very difficult to decide. Specimens from north- 

 ern Norway seem to be more coarsely sculptured and to have a still weaker 

 hinge than specimens from the California coast. The name decussata has 

 been in use for Pacific specimens for many years, and they certainly are 

 very closely related to the Atlantic species. 



Occurrence: Living specimens are recorded in depths from 5 to 144 fms, 

 from a bottom of sand or mud. 



Distribution: Valves are found from Canal de Dewey, Baja California, 

 northwards, while living specimens are recorded from San Clemente 

 Island, California, north to Alaska. 



Genus SOL AMEN Iredale 1924 



Solarnen Iredale, Proc. Linn. Soc. New South Wales, vol. 49, 1924, 



p. 198. 

 Type of genus: Solarnen rex Iredale 1924 (monotypic). 

 Remarks: In the diagnosis, Iredale says that the anterior margin is lower 

 and more sinuate than the posterior, but his figures of S. rex (PI. 33, 

 fig. 15; PI. 35, fig. 2) seem to show the opposite condition. Arcoperna 

 recens Tate 1896 is very close to S. rex. 



The common and well known species Crenella Columbiana Dall 1897 

 seems to have its place in the genus Solarnen, though the young specimens 

 have distinctly thickened and crenulated margins below the umbones. 

 Crenella me gas Dall 1902 seems to have been based on an extremely large 

 specimen of C. columbiana, even though the type locality of C. megas is 

 much farther south than C. columbiana is reported to occur. Crenella 

 rotundata Dall 1916 is perhaps founded on a young specimen of C. colum- 

 biana, but a careful study of the types is needed before C. megas and 

 C. rotundata can be considered synonyms of C. columbiana with certainty. 



