39 2 
MOLLUSCS 
shell. The most interesting feature in connection with these oceanic snails is the 
curious lloat which they construct to support their egg-capsules. It is a sort of 
gelatinous raft, enclosing air-bubbles which cause it to float at the surface; and is 
attached to the foot, the egg-capsules being suspended from its under surface. The 
violet-snails feed on various kinds of jelly-fish, and occur in shoals on the high seas. 
Being unable to sink, so long as they are in connection with their floats, they thus 
escape from storms and are often cast ashore in immense numbers. The species 
are few, and, like other pelagic forms, are widely distributed. Recluzia, the only 
other genus in the family, has a pale brownish shell with a longer spire than 
Ianthina. It likewise forms a raft. The shells of the wentle-traps ( Scalariidct ) 
are mostly white, and formed on the same plan. The spire is more or less 
elevated, the aperture entire, and the whorls are ornamented with a succession 
of ribs or varices which give the shells a pretty appearance. The animals are 
carnivorous. More than one hundred and fifty species are known, and they occur 
in all seas, as far north as Greenland. Four inhabit the British shores, one 
(Scalaria communis ) being the most prettily coloured shell of the genus. S. 
pretiosa, a native of the China Seas, is the largest member. It was formerly 
of value, between twenty and thirty pounds having been given for a specimen. 
SECTION GYMNOGLOSSA. 
This, the last of the five sections into which the Pectinibranchs are divided, 
is characterised by the absence of the radula. Two families are included in it, 
namely, the Eulimidce and Pyramidellidce. The former have white, polished, 
pointed shells, with an ovate aperture, closed by a thin, horny operculum. Many 
of them are curved in the course of growth. Some are known to live commensally 
or parasitically upon or within various species of holothurians. Stylifer, which 
lives in or upon star-fish and sea-urchins, usually has a thinner and more glassy 
shell than Eulima, and has no operculum. A few species are found in Britain, 
but the family is more numerous in warmer latitudes. In the second family the 
majority of the species are very small; and while all are dextral in the adult state, 
the young shells are remarkable for having the nuclear whorls sinistral. Some are 
longitudinally plicate, others transversely ridged, cancellated, or smooth, and the 
columella often exhibits one or more plaits or denticles, which are conspicuous in 
some and almost obsolete in others. The diversity of form and surface ornamenta¬ 
tion, in the very numerous species of this and many other families, can only be 
seen in a collection of specimens, or a good series of illustrations. About forty 
species are British, none of which belong to the typical Pyramidella. 
Suborder Heteropoda. 
This group is regarded by some systematists as a distinct order, and by others 
merely as a division of the Pectinibranchia; and it sometimes appears under the 
name of Nucleobranchiata. It includes gastropods modified for a pelagic life. 
The foot, in place of being adapted for crawling, is laterally compressed, and serves 
the purpose of a fin, and is also used as a means of attachment to the prey or any 
floating substances. The Heteropods are found on the high seas in every warm 
part of the globe. They have distinct sexes, are predatory in their habits, feeding 
