332 THE PRICKLY CHITON. 
The form of the shell is extremely variable, depending greatly on the substances to which it 
adheres, and the color seems to be quite as mutable as the form. A specimen in my posses- 
sion has an exceedingly thick shell, with very deep ridges, and a boldly waved edge. Its 
color is brown, of various shades, diversified with a little ochreous yellow. The ‘‘cup”’ is 
very much lighter than the interior of the shell, and is of a grayish-white with a slight yellow 
tinge, and marked with wavy streaks that give it a singular resemblance to chalcedony. The 
substance of the cup is very delicate, hardly thicker than the paper on which this account is 
printed. 
The species called Lapy’s Bonnet (Calyptrea equestris) belongs to the same genus. The 
generic name is derived from the word calyptra, which signifies a lady’s cap. The food of 
these mollusks seems to be rather varied, as they are known to eat the minute algze, and one 
specimen has been observed in the act of devouring a little sea-slug which we placed in the 
same vessel. 
The HunGartan Bonnet Limpert is almost invariably found adhering to oysters in a 
moderate depth of water, varying from five to fifteen fathoms, though it sometimes prefers a 
greater depth. The finest specimens are, however, taken in the shallower waters. The popu- 
lar name is sufficiently appropriate in this instance, as the shell is exceedingly like the cele- 
brated Phrygian bonnet of the ancients, or the republican cap of a later period. 
The Common Limpert is so familiar that it need not be figured nor described. One 
species of its genus attains to an enormous size, measuring a foot in diameter, and having a 
shell of very great thickness. 
Tue next family, called appropriately Dentalidee, or the Tooth-shells, have long puzzled 
zoologists to assign their right position in the scale of nature, and even bafiled the wide expe- 
rience and penetrative acuteness of Cuvier himself. The general opinion of the systematic 
naturalists of his time referred the Dentalidee to the annelids or worms ; but Cuvier always 
expressed his doubts as to the accuracy of their views, and remarked that the solution of the 
problem would be found in the nervous and respiratory systems. 
Sub-class Secaphopoda is one of the late divisions, embracing the Tooth-shells, so called 
irom their resemblance to long teeth. There are not many, but certain characters render 
them of especial interest. They are the lowest in rank, being the most closely allied to the 
Acephala, The Dentalium was a favorite object with the aborigines of the west coast of 
America, its value as wampum, or money, being very great. 
SuPER-ORDER IsoPLEURA, meaning equal-sided. It embraces quite singular appearing 
forms, which are included in three orders. The Chitons are the more familiar of them ; once 
placed in a group as multivale shells. The Chitonidee, or Mail-shells, are appropriately so 
called, because their shells are jointed like the pieces of plate armor. When separated from 
each other, the plates bear a strong resemblance to the joint of a steel gauntlet, and overlap 
each other in a similar fashion, a thick and strong mantle taking the place of the leather. 
There are eight of these plates, and all of them have a somewhat saddle-like shape. A similar 
arrangement may be observed in the lower abdominal plates of many beetles. Each of these 
plates is fixed to the mantle by certain rounded processes from their front edge, and when the 
plates are examined separately the processes will be plainly seen, white and pearly as the 
interior of the shell. 
The genus Chiton is an extremely large one, containing more than two hundred species. 
Some of them are found at a depth of ten or fifteen fathoms, while a few of the smaller 
species are found in eighty or a hundred fathoms of water. 
The PricKLy Curron is remarkable for the array of rather long spines with which the 
movable plates are armed, and which, when the creature contracts itself, give it a curious 
resemblance to the hedgehog. Its color is reddish-brown on the exterior, and pinky-white 
within. Although this shell attains a very great size, a large specimen measuring about five 
or six inches in length, it is not as valuable as in its youth, the curious spines being gradually 
lost as it approaches old age, just as human beings lose their hair, and the shell being by 
