GASTEROPODS 365 
glutinous secretion which hardens in water, and, being filled with 
air-bubbles, constitutes a float. On the under side of this are 
deposited the eggs in rows of little capsules. While attached to 
this float it is impossible for a Janthina to sink, and hence it is 
that so many of these creatures are sacrificed in onshore gales of 
wind. 
J. fragilis. The shell of this species is so brittle and fragile that it 
is very clearly not adapted to a life near shore. It is in reality a pelagic 
species which is occasionally blown ashore during easterly gales along 
ap a a 
ST 
SS 
Janthina fragilis; FL, float; O, ova; Pr, proboscis; Br, branchie; F, foot. 
the Atlantic coast of the United States. Vast numbers of these pretty 
creatures are sometimes encountered far out at sea, floating quietly on 
the surface. When storms drive them upon the beach, they become 
utterly helpless; since their foot is not adapted for crawling upon the 
sand, they soon perish, and their brittle shells are demolished by the 
surf. In Florida the beaches are sometimes fairly lined with Janthina 
shells, which make a band of purple along the high-tide mark as far as 
the eye can reach; then it may be years before they again appear. 
(Plate LXVIII.) 
” FAMILY SCALIDE 
Genus Scala 
The shells of Scala have such a‘peculiar scheme of decoration 
that once seen they can never be mistaken. They are generally 
pure white, with well-rounded whorls, all of which are crossed at 
even distances by greatly elevated and smooth ribs. Hach rib 
represents a rest-period, when the creature thickened the rim of 
the shell-aperture. The aperture is generally round, with a con- 
tinuous lip. The animal has a retractile proboscis and long, 
slender tentacles with eyes at the outer bases, and is a predaceous, 
carnivorous creature. Some Asiatic species of this genus, remark- 
