Page:Natural History, Mollusca.djvu/208

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196
PECTINIBRANCHIATA.—CERITHIADÆ.

an inch and a quarter in length, of a pale bay or drab hue, with prominent ribs, spotted with purple. The animal is blackish-grey speckled with white.

The Wentletraps inhabit rather deep water, and affect a sandy or muddy bottom: hence they are obtained only by dredging. The species just described has been procured at various parts of our coast, but principally on the shores of Devonshire.


Family Cerithiadæ.

This group, as defined by our latest malacologists, includes shells which at first sight appear to be very dissimilar, as the slender turreted Cerithium and the broad-lipped Pelican's foot. The genera are "remarkable for the muzzle-shaped heads and corresponding features of organization of the animals which construct them." They seem to constitute a group intermediate between those comb-gilled Gasteropoda which have entire mouths, and those which are furnished with siphons, partaking of and mingling many of the characters of both.


Genus Aporrhais.

A thick, massive, many-whorled shell marks this genus, subject to much alteration in form as it advances in age. In youth the aperture is simple, slightly angular, with a moderate canal; in adult age the canal becomes lengthened, and the outer margin of the shell is produced into a wide wing-like expansion, the edge of which projects in diverging lobes or finger-like processes.

The animal has a long muzzle; cylindrical tentacles, with the eyes placed on prominences at