THE SMALLER SEA-SHELLS * 195 



or seven whorls, well sculptured, and is of a dark 

 brown color; the sutures are conspicuous. 



There are several other species of these small 

 shells, one of which, Cerithiopsis purpurea^ Cpr., the 

 Purple Cerithiopsis, is reported by Berry as being 

 rather common at Pacific Grove, though the shells 

 are dead. The nodules on the shell are fine, and it is 

 stained with purple, giving rise to the name. 



Bittium filosurn^ Gld., the Threaded Bit- 

 tium, is shown in Figure 190. This line 

 little mollusk may be found in large num- 

 bers by turning over stones at low tide and pjg 190 

 carefully searching for diminutive shells. 

 It is seldom that a dead shell is found in such a posi- 

 tion without a tiny hermit-crab inside, and at first 

 glance it looks as if the shells were running away 

 without any apparent means of propulsion. The 

 shell is shaped like a short, stout thorn, and it varies 

 in length from one-fourth to one-half of an inch. 

 The whitish or brownish whorls are eight or ten in 

 number, and are marked with slight, spiral grooves. 



Bittium esuriens^ Cpr., the Hungry Bittium, is 

 "like a starved filosum^ very narrow, the adult 

 scarcely sculptured." It is found all along the coast. 



Bittium quadrifilatum^ Cpr., the Four-lined Bit- 

 tium, is a southern species. In shape it is a regular 

 but very slender cone, and the whorls are marked 

 with four equal spiral threads which coil over slight 

 cross-ribs. There are several other species of this 

 genus which are occasionally found, and which differ 

 chiefly in the sculpturing of the whorls. 



