330 THE CTENOBKANCHIA. 



subjected to the culinary art, it is well beaten, like a beef-steak, and is then cooked in 

 various ways. 



A similarly shaped shell, but without any perforations on the edge, is the STOMATIA, or 

 FURROWED EAR-SHELL, so called because the place of the holes is supplied by a single groove 

 or furrow. This shell is a native of the hotter seas. Its color is pale reddish-gray on the 

 exterior, and pearly within. 



A VERT curious snail-like shell is the VIOLET SNAIL (Janthina communis), so called from 

 the beautiful violet-blue of the shell. 



The Violet Snail inhabits several seas, and is most common in the Atlantic Ocean, though 

 it is also found in the Mediterranean. Though in the look of the shell there is nothing 

 sufficiently remarkable to attract notice, the habits and structure of the animal are most 

 curious and interesting. The Janthina is essentially a surface species, always floating about, 

 incapable of directing its course, and not even able to sink when threatened with danger. 

 Being quite at the mercy of the winds and waves, it is often seen floating in great numbers, 

 thus denoting the existence of some aerial or marine current, and may in such cases be swept 

 up by thousands. 



The food of the Janthina is said to consist mostly of the small blue velella? ; but, as the 

 animal is without eyes, and is incapable of directing its course, it cannot be very rapacious. 

 Some minute brown shells have been found in the stomach of several specimens. 



The Janthina secretes a rather richly-colored fluid, respecting which many conflicting 

 opinions have been given. Mr. F. D. Bennett, who has made some valuable observations on 

 this curious mollusk, has the following remarks upon the fluid : 



"The body of this mollusk contains a very blue liquid, which, when the animal is punct- 

 ured, exudes to the amount of three or four large drops. It is readily diffused through water 

 or colorless spirit to the former it communicates a faint tinge of its own peculiar hue, and to 

 the latter a pink color, with a purple shade. It communicates its color to paper, and may be 

 conveniently used as a blue ink ; several memoranda and pages of my journal, written with 

 this fluid, have, after a lapse of more than five years, retained their original appearance both 

 in color and intenseness. For this use, however, it must be employed from the recent animal, 

 as it will not keep in any quantity, but becomes thin and discolored. 



"It is believed that this fluid is analogous in use to the black secretion which the cuttle- 

 fish pours forth to obscure the water and elude the pursuit of its enemies ; but this opinion 

 must be received with some qualification. The living examples of Janthina which I have irri- 

 tated when they have been confined in a vessel containing sea- water have not emitted any of 

 the colored fluid ; when taken in hand, they would sometimes allow a little to exude ; but the 

 entire quantity obtained from one animal by artificial means was never sufficient to cloud or 

 obscure, although it would stain about half a pint of pure water." 



Order ZYGOBRANCHIA. The Ear-shells (Haliotis\ and the Patellas, Little Knee-pans, etc., 

 are of this order. 



The order CTENOBRANCHIA includes four sub-orders, and embraces some of the hand- 

 somest and best-known of shell-fish. The Janthinas are not familiar in the temperate regions, 

 but the beaches of the tropics are strewn with their cast-off shells at times. They are essen- 

 tially oceanic in habit ; resting, if at all, on the rafts of sea-weed, their long floats of bubbles 

 supporting them safely. These creatures have a rich blue and purple coloring, and seem to 

 have no feature of protective resemblance ; consequently, they would present to hungry fishes 

 a tempting morsel. Their eggs are supported under the raft or float. They have, however, a 

 means of protection that may prove all-sufficient : that of throwing out a thick colored 

 liquid when approached, which stains the surrounding medium, and thus affords a certain 

 means of escape from enemies. An excellent figure of Janthina with its float attached is seen 

 in the group of Ear-shells. 



The well-known Volutes, Olivas, Murices (Rose-buds), Pyrulas (Pear-shells), Buccinum 

 (Trumpets), Purpuras (Purple Shells, that throw out purple liquid for protection), Cones, 

 Naticas, Ovules, Cypreas, Strombi (Conch), the curious Pteroscerods, and the very beautiful 



