304 THE CEPHALOPODA. 



species are of exceeding value for the materials furnished by their shelly coverings Some 

 species, where the shell is of that lovely nacreous nature which we popularly term mother-of- 

 pearl, are extensively empbyed in the manufacture of "pearl" buttons, handles to pocket- 

 knives, ornamental utensils, and in the inlaying of costly furniture; and even pearls themselves, 

 the most precious offspring of the ocean, are composed of the same substance as the nacreous 

 coating of the shell; other shells are largely used in the manufacture of cameos, their alternate 

 coats of creamy white and rich red or warm brown giving beautiful artistic effects when skil- 

 fully handled. 



In former days, one of the univalve shells, known now as the purpura, and little 

 heeded except by the owners of marine aquaria, was employed for the purpose of producing 

 the celebrated purple of the ancients, which none but the imperial family were permitted to 

 wear. 



Shells have in former times been valued at fabulous prices. Collectors were merely such 

 for the pleasure of owning beautiful things and not for purposes of science ; consequently the 

 shells became important objects of commence. 



In 1735 the Scalaria pretiosa, which now is sold for about two dollars, then was worth 

 one hundred dollars, and earlier two hundred dollars. Several of the Cypeas were held at 

 one and two hundred dollars. The celebrated Orange Cowrey, in our day, has been held at 

 fifty dollars each. The Cones are proverbially valuable even now. Several species, and the 

 Volutes, have commanded over one hundred dollars each. 



The Argonauta argo when perfect is a most elegant thing. One in the Boston Natural 

 History Society's Cabinet was purchased for five hundred dollars. Its size is about three 

 inches greater, in diameter, than any other known. 



Having now taken a superficial glance at the Mollusks and their uses, we will proceed to 

 the description of individuals, and examine closer into details. 



CEPHALOPODA. 



THE highest of the mollusks are those beings which are classed together under the title of 

 CEPHALOPODA. This is a term derived from two Greek words, the former signifying a head, 

 and the latter a foot, and it is applied to these creatures because the feet, or arms as they 

 might also be called, are arranged in a circular manner around the mouth. 



In these animals, which are, as has already been mentioned, thought by many naturalists 

 to be above the mollusks, the organization is highly developed. The nervous system is more 

 like that of the vertebrates than is the case with any other kind of mollusk, the knot of 

 ganglia in the head bearing no small resemblance to a real brain. The Cephalopods breathe by 

 means of a pair of gills or branchiae, one set on each side of the body, and the circulating system 

 by which the blood is driven through those organs and thence to the remainder of the structures 

 is very complete. 



They are all animals of prey, and are furnished with a tremendous apparatus for seizure 

 and destruction. Their long arms are furnished with round, hollow discs, set in rows, each 

 disc being a powerful sucker, and, when applied to any object, retaining its hold with wonder- 

 ful tenacity. The mode by which the needful vacuum is made is simple in the extreme. The 

 centre of the disc is filled with a soft, fleshy protuberance, which can be withdrawn at the 

 pleasure of the owner. When, therefore, the edges of the disc are applied to an object, and 

 the piston-like centre withdrawn, a partial vacuum is formed, and the disc adheres like a 

 cupping-glass or a boy's leather sucker. 



These discs are all under the command of the owner, who can seize any object with an 

 instantaneous grasp, and relax its hold with equal celerity. The arms are almost as movable 

 and as useful to the cuttle-fish as the proboscis to the elephant, for beside answering the 



