Cowry and Pyramid-shells 239 



tlie tentacles are awl-shaped, and the eyes are placed 

 on little prominences at their outer base. The sexes 

 are distinct. The Common species, 



B. reticulatuin, figured here, is about 

 half an inch long, of a reddish-brown 

 colour. It feeds upon decaying 

 animal and vegetable matter, and 

 abounds on all our coasts between 

 half-tide and about 15 fathoms. The ""''(eni'ge'dT'''' 

 Reversed Horn-shell (Tr if oris ^^er- 



versa) is a smaller shell with the spiral turned in the 

 opposite direction. B. reticulatuvi, like most spiral 

 shells, has the open mouth on the right hand of the 

 observer when the shell is held with the spire upwards ; 

 in T. perversa the mouth is to the left hand. It is 

 by no means so plentiful as B. reticulatiiin, and is 

 found chiefly on our southern and western shores, in 

 the Channel Islands, and all round Ireland. It is 

 found sparingly in Scotland, the Oi-kneys, and Shet- 

 land. Its range is from low water to about 20 

 fathoms. The Obelisk-shell (Lovenella Qiietula) is a 

 third species, of whitish hue, about three-quarters of 

 an inch long, found rarely on the Shetland fishing 

 banks in from 45 to 96 fathoms. 



Another group of Horn-shells is placed in a separate 

 genus Cerithioi^sis, — that is having a likeness to 

 Cerithiu7)i, — and these are chiefly distinguished by 

 the groove at the base of the mouth being developed 

 into a distinct though short canal, which is lined by 

 the mantle tube or branchial siphon. The British 

 species are G. tubercular is, 0. harleei, C. pulchella, 



C. onetaxce, C. concatenata, and C. costulcJa. 



The only example we have of the Screw-shells 

 16 



