3362 THE MOLLUSKS OR SHELLFISH 



shell. The most interesting feature in connection with these oceanic snails is the 

 curious float which they construct to support their egg capsules. It is a sort of 

 gelatinous raft, inclosing 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 jellyfish, 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 lanthina. It likewise forms a raft. The shells of the wentletraps 

 (Scalariidce) 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 suc- 

 cession 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 colored shell of the 

 genus. S. pretiosa, a native of the China Sea, is the largest member. It 

 was formerly of value, between one hundred and one hundred and fifty dollars 

 having been given for a specimen. 



SECTION GYMNOGLOSSA 



This, the last of the five sections into which the Pectinibranchs are divided, is 

 characterized 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 

 starfish 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 ornamentation, 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 



