554 LEPADID.E. 



large horny disc attached to the cavity, it cannot keep its 

 body straight during the long-continued boring process. 



The animal is attached by its horny disc to the thin shelly 

 roof over the peduncle, and likewise to the under side of the 

 narrow end of the fissure, but is elsewhere quite free. I 

 carefully examined the disc in many specimens, but could 

 not see any cement-ducts : I believe I saw layers of cement 

 at the upper end of the disc, but it is not easy to discrimi- 

 nate between this substance and the yellowish, somewhat 

 disintegrated, layers of the horny disc. The pupa cer- 

 tainly becomes attached by ordinary cement, so that the 

 attachment in early life, at least, is normal. In some full- 

 grown specimens, I found the lower parts of the horny disc 

 attached, alone; the edges of the layers, to the roof of 

 shell ; and as I looked here in vain with the highest 

 powers for cement-ducts, or for cement, it appears to me 

 probable that the rough edges of these layers were 

 united to the roof by a thin layer of the inorganic calcareous 

 deposit. The animal, from its very protected situation, 

 certainly requires to be less firmly cemented than other 

 cirriped.es ; and even in Lithotrya, which is less deeply im- 

 bedded than Alcippe, the cementing apparatus was feebly 

 developed. From the length of the pupal antennae, cemented 

 by their terminal segments, the position of the young 

 cirripede (PL 22, fig, 12) can be changed to a considerable 

 extent, like a ship swinging at her moorings, but in order 

 to assume its final position, the animal must, I think, travel 

 like Lithotrya, but to a much less extent, by a short succession 

 of overlapping horny discs, — the old discs being partially de- 

 serted, each new one extending beyond the last-formed one : 

 even in the case of the mature animal, we have seen that, 

 under certain circumstances, it changes, to a certain extent, 

 its position ; portions of the old disc being deserted and 

 attached to the roof of a deserted portion of the cavity. 



Affinities. — In the preliminary remarks under the Family, 

 I have discussed this subject almost sufficiently : I will here 

 only remark, that the genus, though so abnormal, yet 

 stands naturally between Ibla and Anelasma, having clear 

 affinities, on the one side, through and bevond Anelasma to 

 Alepas ; and on the other side, beyond Ibla to Scalpelluin, 



