304 THE CEHEPHALOPODA. 
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 employed 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. 

CEPHALOPO© DA: 
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 toa real brain. The Cephalopods breathe by 
means of a pair of gills or branchize, 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 
dise 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 dise is filled with a soft, fleshy protuberance, which can be withdrawn at the 
pleasure of the owner. When, therefore, the edges of the dise are applied to an object, and 
the piston-like centre withdrawn, a partial vacuum is formed, and the dise 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 
