332 THE PRICK LT 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 LADY'S BONNET (Calyptrcea 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 algae, and one 

 specimen has been observed in the act of devouring a little sea-slug which we placed in the 

 same vessel. 



The HUNGARIAN BONNET LIMPET 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 LIMPET 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. 



THE next family, called appropriately Dentalidse, or the Tooth-shells, have long puzzled 

 zoologists to assign their right position in the scale of nature, and even baffled the wide expe- 

 rience and penetrative acuteness of Olivier himself. The general opinion of the systematic 

 naturalists of his time referred the Dentalidse 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. 



Sab-class Scaphopoda is one of the late divisions, embracing the Tooth-shells, so called 

 from 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 Chitonidse, 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 CHITON 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 



