CLASS-BOOK OF ZOOLOGY. 167 



called, from their appearance, Sea-grapes, or Sea-hop ; 

 whilst in others they form a long row of horny, flat cap- 

 sules, which lie close to one another, fastened by one 

 edge to the rib, which is a foot long. 



5 725. The genus Periwinkle (Helix) consists mostly 

 of land and fresh-water snails, many of which are used 

 as food. 



§ 726. The Cuttlefish (Sepia) has a cylindric body in 

 a wide open cloak, and is covered on the back with a 

 shell or plate of the form of a lancet. From the cloak 

 projects a thick head with two large eyes, and a number 

 of fleshy arms surround the mouth, which has the form 

 of a parrot's bill. 



§ 727. The processes on their arms, which in some 

 species exceed a thousand, increase with the age of the 

 animal, and are reproduced when nipped off by fishes. 



§ 728. Most of the species are remarkable for the 

 blackish-brown fluid, contained in a particular receptacle, 

 which they eject at pleasure, and by that means darken 

 the water around them ; thus making themselves in- 

 visible to an approaching enemy. This black substance 

 formed the ink of the ancients, and is probably the 

 principal ingredient of the Chinese or India ink. 



§ 729. Some of these species, as the Calmar, (Sepia 

 Loligo,) are used as food by some people ; but they seem 

 designed principally as food for fishes : The Calmar is 

 seen in such quantities in the seas of Newfoundland and 

 Labrador, as literally to cover the surface of the water, 

 and forms, in the month of August, almost the only food 

 of the Codfish. 



§ 730. The Cuttlefish are found in most parts of the 

 ocean. Their length is from one inch to several feet, 

 according to the species ; as, for instance, the Eight- 

 armed Cuttlefish, (Sepia Octopoda.) found in the East 

 Indies, as well as in the Gulf of Mexico, which is six 

 feet long, and eatable ; but dangerous, however, to those 

 who are bathing, on account of its long and strong 

 arms. 



§ 731. The Common Cuttlefish,, (Sepia officinalis,) 

 about ten inches long, is found in the Mediterranean, 



