Page:Natural History, Mollusca.djvu/178

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166
PECTINIBRANCHIATA.—CYPRÆADÆ.

chiffonier, my readers will be at no loss for the means of actual comparison of the following characters by which it is distinguished. The shell is oval, more or less swollen, and flattened on the inferior side: its surface is polished or enamelled, commonly smooth, but sometimes marked with parallel grooves: the aperture is as long as the whole shell, narrow, forming a canal at each extremity; the outer lip is in full age bent inward, and much thickened, and as well as the inner lip, (or that edge of the aperture which faces it,) in almost all the species marked with numerous parallel tooth-like ridges.

The animal has large smooth, or warted mantle-lobes, capable of entirely embracing the shell between them, their edges meeting along its summit. The head is broad, with a retractile proboscis, and long, pointed tentacles, at the bases of which are the prominences which carry the eyes. The jaws are horny, and there is a long ribbon-like tongue, armed with rows of minute-teeth.

Some species appear to have the faculty of changing the colours with which the mantle is vividly adorned. Mr. Stutchbury, who had an opportunity of examining many individuals of C. tigris at the Pearl Islands, has stated that those cowries lived there in very shallow water, and always under rolled masses of madrepore. They never were to be seen exposed to the sun's rays. On lifting one of those masses a tiger-cowry was generally observed with its shell entirely covered by the large mantle, which was mottled with dark colours, the intensity of which the animal seemed to have the power of changing; for the colours varied in the same light and in the same medium,