ANELASMA SQUALICOLA. 171 



The Peduncle is about half as long as the capitulum, 

 but, according to Loven, this part varies in length ; it is a 

 little narrower than the capitulum; colourless, from being 

 imbedded in the shark's skin ; sub-globular ; basal end 

 almost hemispherical. Total length of animal 1*3 J dia- 

 meter of peduncle *4 of an inch. 



The external membrane of the capitulum is not nearly 

 so thick as is usual in other Cirripedes, and is, therefore, 

 unusually flexible. The internal membrane, on the other 

 hand, is very much thicker than is usual, being only a 

 little thinner than the outside coat ; this circumstance, as 

 well as the similarity in colour on both sides, is evidently 

 due to the remarkable openness of the sack, and conse- 

 quent exposure of its inside. The inner membrane, 

 when viewed under a high power, is seen to be covered 

 with the minutest spines ; the external membrane is 

 structureless, except that there are a few rows of very 

 minute beads of hard chitine, like those which occur on 

 the capitulum of Conchoderma aurita. Loven, however, 

 states that there are imbedded in the outer membrane, 

 scattered, minute, dendritic, calcareous particles. Of 

 these, I could see no trace. There is a very thin muscular 

 layer between the two coats, all round the capitulum, and 

 this layer becomes rather thicker round the base, near the 

 peduncle. The adductor muscle, occupying its usual 

 place close below the mouth, is thinner than in any other 

 Cirripede of the same size seen by me ; nor does it end so 

 abruptly at each extremity, as is usual : where attached 

 to the outer coat, no impression is left. It is a singular 

 fact, that in this Cirripede alone, the fibres of the adductor, 

 and of the muscles of the cirri, and of the tropin of the 

 mouth, are destitute of transverse striae ; but it is not 

 singular, that the muscles surrounding the capitulum 

 should, also, be destitute of striae, for this is the case 

 with the muscles which, running up from the peduncle, 

 surround the capitulum in Alepas, and partly surround 

 it in Conchoderma. It must not be inferred from the 

 absence of transverse striae in the muscular fibres of the 



