TESTACEA. 25 



shagreen, consisting of numerous circular low prominences. Eighteen 

 tufts, each composed of thirty-five or forty bristles, half a line long, like 

 a stout thick brush, invest the margin of the shell, which consists of 

 seven transverse plates. The animal is brown ; head and body distinct. 

 It consumes soft red rock ; and gnaws the paper covering of its vessel. 

 This last substance is likewise devoured when purposely introduced along 

 with the animal. The motion of the creature is very slow. It adheres 

 firmly and tenaciously to subjacent objects. The smoothness of the glass 

 seems to allure above the surface of the water. But it wiU generally de- 

 scend when left dry. 



Plate V. 



Fig. 13. Chiton fascicularis, upper surface. 

 ] 4. The same, under surface. 



2. Chiton vulgaris. — Plate V. Figs. 15, 16. 



Length of the shell between seven and eight lines. Figure oval, 

 composed of eight transverse plates, with a flat narrow margin, surround- 

 ed by a very short fringe. Surface like shagreen. Colour grey. The 

 animal is dingy white. 



It feeds on the common gi'een fucus, copiously on the larainaria or 

 tangle, and it may be occasionally found in considerable abundance on 

 the shore where this substance is common. I have not observed it con- 

 sume any animal matter. 



The motion of this creature is very slow, the flexible nature of the 

 shell and the transverse plates being free to slide on each other, admit 

 of various curvatures, adapting the body to the irregular surfaces ou 

 which it dwells. 



Spawn, consisting of numerous ova amidst albuminous matter, has 

 appeared in the middle of October. 



The common Chiton survives readily during a long time. As the 

 plates of the shell are not connected b}'^ any Ugament, they may be sepa- 

 rated with facility after it dies, when their peculiar form is discovered to 

 be diff'erent from what the superficial observer would infer. 



Plate V. 



Fig. 15. Chiton vulgaris, upper surface. 

 16. The same, under surface. 



