26 TESTACEA. 



Note. Several species, which are but indistinctly characterized, in- 

 habit the Scotish coasts, both mainland and islands. 



Some of those are represented, Plate V. figs. 15, 16, 17, 18, 19. 

 But none of them exhibit any peculiarities, or any very decided charac- 

 ter. Indeed, I am induced to conclude, that on the whole, except in a 

 few points, the Testacea are among the least interesting products of the 

 creation. 



Fig. 17, a native of Shetland, of angular form, is universally speckled 

 and mottled, chiefly reddish-brown and dingy-yellow. The marginal 

 border is divided into oblong rectangular darker and lighter compart- 

 ments. 



This animal dwells on rocky substances without apparent vegetation. 

 Several individuals seated on a portion of such a rock, survived many 

 months, continuing quite plump and vigorous. Numerous white pellets 

 were discharged in their vessel. 



These receded very slowly from the light. If the rocky fragment was 

 reversed, so as to expose them below, they were afterwards found to have 

 descended. The Chiton shifts its position slightly and rarely. Here the 

 great inequalities and cavities of the surface of the rocky substances 

 proved the flexibility of the plates of the shell. 



PLATE V. 



FIG. L7. Chiton ruler. 



18. Chiton Icevia, upper surface. 



2. PATELLA. The Limpet. 



A very comprehensive group among the Testacea was instituted by 

 the earlier naturalists as the Patella, derived from the resemblance of 

 the shell of various species to different utensils employed in domestic 

 economy. 



This group has undergone several subdivisions, according to the 

 views of later naturalists. But as yet no solid basis has been assumed 

 for permanent arrangement, thus leaving much perplexity regarding the 

 proper position of certain species in the Systema. 



