SHELLS WITHOUT CANALS 



213 



Natica clausa, Brod. and Sby., the Closed Natica, 

 is tound on the coast of British Columbia, and in 

 northern waters generally. It resembles Figure 204, 

 but it is easily distinguished by its closed umbilicus 

 and its shelly operculum. 



A m pullina purpurea^ 

 Dall, the Purple Moon- 

 shell, Figure 206, has a 

 purplish shell, though the 

 ])atches of enamel near the 

 aperture are white, while 

 the periostracum is olive, 

 with darker streaks. It 

 reaches a length of two 

 inches and it is found in 

 northern waters, as far as 

 Point Barrow. 



Sinum debllis^ Gld., the 

 Frail Sinum, {Sigaretus 

 debilis)^ has a delicate, pure 

 white shell, very flat, with 



a small spire and a very large aperture. The shell is 

 beautifully sculptured with line ra^^s crossing the 

 lines of growth. Its breadth is an inch or more, and 

 its home is in the south. 



Eufiaticina oldroydii, Dall, Oldroyd's Natica, re- 

 sembles Figure 204 in shape, and it is marked with 

 almost microscopic sculpturing. It has been dredged 

 at several places along the California shore, but is 

 still a rare species. Compared with Polynices lewisii 

 its shell seems very thin and delicate, indicating that 

 it lives in deep and quiet water. The diameter is 

 about an inch and a half. 



Fig. 206. X ■;: (*) 



