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, Fag. 109), 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 littorea. 
The Floating Snail, (Janthina 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 up upon our shore by southerly 
gales. The shell is blunt and about one 
and a half inches in width, 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 usually broken by 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 
Fig 110; FLOATING SNALL. 
a ae. oe Rea ae acne 
even deposits her eggs in spindle-like mete aaoae 
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 
