PATELLA. 261 



debarred access to marine vegetables ; their recorded descents 

 from high levels, and periodical exits from,, and returns to, 

 the identical hollows they have made, after feeding on algae, 

 have almost a fabulous complexion ; zones of sand fifty yards 

 wide often intervene between them and such food, and their 

 exceedingly slow locomotion is opposed to such manoeuvres. 



As these animals are often for long periods prevented from 

 obtaining animalculse from the water, it would appear that 

 they have the power of drawing nourishment from the saline 

 particles floating in the air, and extracted from their porous 

 habitations. This idea is in some measure confirmed by the 

 fact, that in all the animals I have observed of this species 

 the intestine has always been filled with sand. I am now 

 speaking of isolated individuals, which, however, are frequent 

 and of all sizes. The great mass of the P. vulyata in the 

 lower levels have the means of obtaining submersion and 

 vegetable food. 



P. ATHLETICA, Beail. 



P. athletica, Brit. Moll. ii. p. 425, pi. 61. f. 7, 8. 



The anatomy and external organs of this species scarcely 

 differ from those of the P. pellucida, and as they have a still 

 greater similarity to the P. vulyata, with which it has long 

 been confounded, I will describe the principal variations, 

 which, however, constitute sufficient specific distinction. The 

 animal differs from P. vulgata in its much lighter colour, and 

 in the substitution of the shades of orange-yellow for the lead- 

 or pale smoke-brown. The mantle is edged with flake-white 

 pointed filaments, twice as short and thick as in its congener. 

 The branchial plates are longer, thinner, paler, and more arcu- 

 ated at the terminations. The foot is of the various hues of 

 orange-yellow, with scarcely any anastomosing lines. The 

 head is of the palest purple ; the tentacula pale yellow, shorter 

 and more slender than in P. vulgata. I do not, except in par- 

 ticular cases, regard colour of much distinctive aid, but here 

 the organic deviations corroborate this dubious character. 



This species has long been known on the Devon coast as 

 the China Limpet, from the rich porcellanous interior aspect, 



