POWERS OF BURROWING. 343 



The membrane of the peduncle is continuous with the 

 yellow membrane coating the external surface of the cup ; 

 and this latter membrane is continuous with those delicate 

 laminae which, in a calcified condition, form the layers of 

 the cap itself. In an exactly similar manner, in this and 

 other cirripedes, the membrane of the peduncle, at the 

 top, is continuous with that coating the valves, and is 

 attached to the lower exterior edge of the last-formed 

 layer of shell. When a new shelly layer is formed, both 

 under the valves of the capitulum and inside the basal 

 calcareous cup, it projects beyond the old layer, and is 

 included within the old, as yet not moulted, membrane of 

 the peduncle. Within the cup of L. Nicobarica I found 

 a lately-formed layer of shell, projecting ^th of an inch on 

 one side of the cup, and by its protuberance distinguish- 

 able even through the old coat of the peduncle, which was 

 nearly ready to be moulted. In an analogous manner, 

 in the capitulum of L. dorsalis and L. truncata, I have 

 found a new peduncular membrane bearing the usual, 

 but then sharp, calcified scales, attached to the lower pro- 

 jecting edge of the last-formed shelly layer, lying under 

 the old peduncular membrane, which was attached to the 

 penultimate layer of shell, and with its worn scales was 

 just ready to be moulted. 



The final cause of the moulting of the calcified scales, 

 together with the membrane of the peduncle to which they 

 are attached, — a case confined to Lithotrya, — I have 

 scarcely any doubt is the reproduction of a succession of 

 scales, sharply serrated for the purpose of enlarging the 

 cavity in which the animal is lodged. The extreme thinness 

 of the membrane of the peduncle has been noticed ; this 

 may be partly related to its protected condition, but partly, 

 I think, to the necessity of its being formed in a very 

 extensible condition ; for the new coat, owing to the pro- 

 jection of the new shelly layers under the valves, and 

 within the basal cup, is by so much shorter than the old 

 peduncle, yet after exuviation it has to stretch to a greater 

 length than the old membrane, to allow of the growth of 



