82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



The genus Solamen, which perhaps will be shown to be a subgenus of 

 Crenella Brown, comprises two Australian species, one species from Java 

 (Solamen sibogae Prashad 1932), and three Japanese species; and per- 

 haps a few other species of Crenella should be referred to this genus. 



Solamen columbianum (Dall) 1897 

 Plate 8, fig. 46 ; text-figs. 66-68 



Crenella columbiana Dall, Bui. Nat. Hist. Soc. British Columbia, vol. 2, 



1897, p. 4, PI. 1, figs. 3 and 5. 

 Syn.: f Crenella megas Dall 1902. 



? Crenella rotundata Dall 1916. 

 Holotype: U. S. National Museum. Cat. no. 107630. 

 Type loc.: Chernoffski, Unalaska; 109 fms. 



Remarks: This species and perhaps also the type of the genus, S. rex 

 Iredale, have fine radiating striae separated into three areas, as in Cren- 

 ella, by slight differences in the sculpture. The anterior part is separated 

 from the main part of the shell by a smooth narrow stripe ; the radiating 

 striae anterior to this smooth stripe fork out from it. There is also an 

 irregular, partly smooth stripe on the posterior part, with lateral forking 

 of the striae anterior to it. The radiating striae on the median part do not 

 fork, but have some striae in the interspaces in the younger parts of the 

 shell. 



The short ligament is not situated in an inwardly sloping groove, but 

 placed on thin nymphae with a resilial ridge. Margins are most conspicu- 

 ously crenulated in the anterior part, with no thickening below the umbo. 

 There are tooth like crenulations in larger specimens. Specimens with a 

 length of 6 mm have the same vertically thickened, striated subumbonal 

 part found in species of Crenella, and can be separated from them only 

 by the finer striae and thinner shell. The form is round in small speci- 

 mens, with a shining white prodissoconch. As the animals grow, they 

 become more elongate and the posterior part is attenuated (megas Dall). 

 One large specimen measures 21.5 mm in length, 15 mm in height, and 

 14.2 mm in diameter, and the largest specimen (broken) has a length of 

 at least 22 mm. Dall says the extreme length is 16 mm. 



The figure of a 15 mm specimen (Dall, 1897) is not much like the 

 figure (Dall, 1925, PI. 9, fig. 1) of a young shell, which seems to have 

 broader ribs with linear interspaces. Young shells, however, look rather 

 different from larger ones, for the white color and less inflated form 

 make the ribs look broader. But as the large, white, smooth prodissoconch 

 is the same size, it seems reasonable to consider them all the same species. 



