CHAM^SIPHO COLUMNA. 471 



Hah. — New South Wales, Tasmania, New Zealand ; extremely common ; 

 attached to littoral shells and rocks ; often associated with Chthamalus antennatus 

 and Elminius modestus ; and in New Zealand, often thickly coating Elminius 

 plicatus. 



I have identified, with some doubt, the present species 

 with the Lepas columna of Spengler, obtained from Ota- 

 heite, as no description is given by him of the opercular 

 valves, and more especially as Spengler's specimens were 

 an inch in height and seven lines in width, which is much 

 larger than any of the many specimens seen by me : from 

 Spengler's clear description of the structure of his shell, it 

 evidently belongs to the present genus. 



General Appearance and Structure of Shell. — The sutures separating 

 the four compartments are generally, excepting at an early age, quite 

 obliterated, both internally and externally, the shell in this case con- 

 sisting of a single piece, with its summit and opercular valves always 

 much worn. Occasionally the sutures are preserved, and then the four 

 compartments are seen to be of nearly equal sizes. The orifice is 

 always broadly oval, with the carinal end the broadest ; and it often 

 approaches closely to circular. The upper part of the shell is fre- 

 quently steeply conical, with the lower part spreading and folded; 

 sometimes deeply folded. Very young shells are apt to be remarkably 

 smooth. The radii appear never to be developed : the inside of the 

 shell is smooth. The colour is either blackish-green (this being the 

 tint of the corium lining the sack), with the upper part gray from dis- 

 integration ; or the lower part is brown, from the investing membrane, 

 the shell itself being pale coloured. This species seems particularly 

 liable to grow crowded together ; often covering rocks and shells with 

 a honey-combed layer. The basal diameter of some of the largest 

 specimens was - 3 of an inch. In Mr. Cuming's collection, however, 

 there is an Australian specimen "55 in diameter and '3 in height, 

 which is, moreover, remarkable from the projecting, extremely rugged, 

 over-lapping, dark-coloured layers of growth, which surround the lower 

 part of the shell: we have seen that Spengler's specimens, said to have 

 come from Otaheite, are even broader and considerably higher. 



Scuta : from the disintegration which the valves have undergone, 

 the scuta and terga are externally seen to be locked together by a 

 deeply sinuous articulation. The Scuta have a wide articular furrow 

 and a very prominent articular ridge; but the exact outline of these parts 

 varies greatly, very much as in the genus Chthamalus. 



The Terga are very narrow, with the under surface channelled : the 

 attachment of the depressor muscle offers the only peculiarity, — the 

 muscle being attached to four or five little pits, placed transversely to 

 the longer axis of the valve ; the septa between these little pits 

 evidently answering to the crests as usually developed. 



Mouth. — The crest of the labrum is hairy, and slightly bullate. 



