112 CEROSTOMA. 



M. PUTEOLUS, A. Ad. 



Ovately fusiform, spire elate, conical, light fuscous ; whorls 

 five, angulated in the middle ; with squamose, subdistant re- 

 volving lirse, and seven varices ; costately spinose and produced 

 into squamate spines behind; aperture ovate; canal short, open, 

 recurved. 



Japan. 



No dimensions given ; not figured. 



Subgenus Cerostoma, Conrad. 



It is very difficult to define the boundary between this group 

 and Pteronotus, inasmuch as the operculum of several of the 

 species is not known ; moreover the labral tooth does not always 

 appear even in those species having a purpuroid operculum. It 

 is possible that some of the last species of Pteronotus, as I have 

 arranged them, belong in Cerostoma, and on the other hand that 

 some of the first species of Cerostoma may be true Pteronoti. 

 All the species with more than one inter-variceal node appear to 

 be true Pteronoti, and the distribution of the genus is mainly 

 Indo-Pacific ; Cerostoma, on the other hand, is North Pacific in. 

 distribution, extending from Japan northwards to Behring's 

 Straits, and on the opposite American coast south to Central 

 America. In no other group is the difficulty so great in obtain- 

 ing good specific characters. I have been forced to admit a 

 number of species, which my knowledge of specific variation 

 causes me to suspect very strongly to be mere individual varia- 

 tions of form ; a considerable reduction of these may be expected 

 as soon as extensive suites from numerous Japanese localities 

 shall be obtained. 



M. PINNIGER, Brod. PL 34, fig. 318. 



Light yellow or flesh color. Length, 1*75 inches. 



West Columbia. 



Has very close analogies with M. osseus, Reeve, and indeed, is 

 so like the young of that species (M. Gambiensis) that, were it 

 not for the wide difference of locality, I would scarcely hesitate 

 to put them together. Found at Xixipati, in sandy mud, at 8 

 fathoms. 



