THE PRICKLY CHITON. 



403 



WE now come to the curious family of molluscs called appropriately Chitonidae, or 

 Mail-shells, 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 cer- 

 tain rounded processes from their front edge, and when the plates are examined sepa- 

 rately the processes will be plainly seen, white and pearly as the interior of the shell. 



The last plate is thought by Mr. Gray to be analogous to the shell of the limpet, 

 and the seven other plates to be "portions of its anterior slope successively detached." 

 At all events, the hinder plate is fixed more firmly to the mantle than any of the others ; 

 and while its companions fall off with handling, or give way at a slight pull, the hinder 

 plate holds firmly in its place. 



PRICKLY CHJTON.-C/iflofl aculeatus. MARBLED CHITON.- Chiton marmoreus. 



SHORT-SPINED CttlTON.-Chttoa brevlsplaosus. BANDED CHITON. Chitoaellus fasclatus. 



ELEPHANT'S TUSK.Deatallum arcuatum. 



The genus Chiton is an extremely large one, containing more than two hundred 

 species, which are spread over the whole of the globe, wherever the sea is not absolutely 

 frozen. The greater number of species are found on the rocks about low water, and 

 on our own coasts the naturalist may fill his bottle with specimens, provided he examines 

 the proper spots. Some of them are found at a depth of ten or fifteen fathoms, and 

 are obtained by dredging, while a few of the smaller species are found in eighty or a 

 hundred fathoms of water. 



The Chitons are able to roll themselves up in a partial kind of manner, and present 

 a curious resemblance to the well-known armadillo or pill woodlouse. In all these 

 creatures the shell is extremely beautiful, on account of the minutely graceful markings 

 with which it is decorated, and which, in most cases, require the aid of a magnifying 

 glass to exhibit their true beauties. 



SEVERAL species are represented in the engraving. At the top is shown the PRICKLY 

 CHITON, remarkable for the array of rather long spines with which the movable 



