MOLLUSKS 149 



furrows. It can remain out of water for hours at a time without 

 suffering any apparent inconvenience. When the tide comes in, 

 however, it crawls slowly about feeding upon vegetable matter. 

 The foot is black and the head is provided with two sharp-pointed 

 tentacles with eyes on their outer sides near their bases. 



The Seaweed Snail, (Littorina palliata, Fig. 109 J, ranges from 

 New Jersey to Nova Scotia, and is common upon sea weeds between 

 tide limits. The surface of the shell is smooth and is variable in 

 color, being either olive, yellow, or brown, red or mottled, but usu- 

 ally closely approaching the color of the seaweed upon which it 

 lives. The spire is blunter than in Littorina Uttorea. 



TJie Floating Snail, (Jantli'ma fragilis, Fig. 110). This beau- 

 tiful snail is found floating upon the Gulf Stream, and off the 

 Florida coast and West Indies in the spring, but it is occasionally 

 cast Tip upon our shore by southerly 

 gales. The shell is blunt and about one 

 and a half inches in w^idth, and is of a 

 beautiful purple-blue color, lighter over 

 the spire than at the base of the body 

 whorl. It is almost as thin as paper, and 

 is usiially broken l)y the surf in being 

 washed ashore. A gelatinous substance 

 is secreted by a gland in the foot of the 

 animal, and this becomes filled with air 

 bubbles and hardens to form a veritable 

 raft that floats the snail. The female 

 even deposits her eggs in spindle-like ^'^ "°' floating snail. 



^ °° , 1 Tortugas, Florida. 



capsules on the under side of this raft, 



the youngest eggs being nearest the body of the snail, and the old- 

 est on the outer end of the raft. The feathery gills project beyond 

 the lip of the shell, and there are four tentacles upon the head. 

 While the float remains attached it is impossible for the snail to 

 sink, but it may apparently be cast off at will. When pressed the 

 snail exudes a blue-violet fluid. 



The Boat Shells, (Crepidula). These are often called "deck- 

 ers" or "slipper limpets." They are degenerate, scale-like snails, 

 and when full grown either remain fastened permanently to one 

 spot or move very slowly. Those species that become fast to one 



