CHITON. 213 



more sensible of cold than the Littorina, and that even 

 about the middle of November it was difficult for him 

 to find two or three specimens in an hour's search at 

 Tenby, in a spot where he could during the month of 

 August get more than as many dozen in the same time. 

 The fleshy part of the girdle must be porous or vascular, 

 because it becomes swollen and puffed up if confined 

 by a ligature ; it is often raised in folds or puckered, to 

 admit water to the gills. The dorsal ridge is formed 

 by the wearing away of the granulated surface, showing 

 that this part of the shell is never renewed. The plates 

 are frequently encrusted by small spiral Serpulce and 

 Foraminifera, In young shells the triangular compart- 

 ments are to be seen, as in other species of Chiton. 



It may be the " Kalison " of Adanson. The short 

 description by Linne of C. fascicularis, and the 

 habitat (Barbary), are rather more applicable to C. 

 discrepans than to the present species. Writers on the 

 Mediterranean shells have evidently mistaken one for 

 the other. Pennant says his C. crinitus has only seven 

 valves; but his figure shows eight and the usual number 

 of tufts. I am also disposed to refer to C. fascicularis 

 the Acanthochites aneus of Eisso, and certainly the 

 Acanthoch&tes vulgaris of Leach. I cannot maintain 

 the distinction which at first seemed to exist between 

 the typical form and the variety gracilis, and which in- 

 duced me to describe the latter as a separate species. 

 Both have every character in common, except the ad- 

 ditional tuft ; and that is not constant. 



