MOLLUSCA 



235 



kingcrabs; they have a sort of shelf on the inner side of the 

 shell. The sea ears, or abalone shells as they are called in Cali- 

 fornia, have a beautifully iridescent, pearly lining. The row 

 of holes in the shell is produced by the edge of the mantle, 

 as the shell increases in size. The strength with which the 

 limpets and sea ears can fasten themselves to rocks and other 

 objects is remarkable. 



A snail of some economic importance on the 











Fir,. 237. Triton nodiferus ; median longitudinal 

 section of shell. (Alter Parker and Haswell.) 



FIG. 238. Vermetus lum- 

 bricahs, a loosely wound 

 spiral shell. (From 

 Brehm's Thierleben.) 



eastern coast of the United States is the drill snail, Urosalpinx 

 cinerea, which bores holes in the shells of oysters and then 

 devours the animal. The whelks are common in Europe and 

 America along the northern Atlantic coasts, where they bury 

 themselves in the sand ; they are largely eaten in England. The 



