TETRACLITA ROSEA. 335 



by a few very small branching ridges. The alee have their edges 

 plainly crenated. The sheath is dark green, with the lower edge free. 



The Mouth presents no particular characters. With regard to the 

 Cirri, I am doubtful whether any confidence can be placed in the 

 numbers of the segments being constant ; but I may state that the second 

 cirrus contained thirteen and sixteen segments in its two rami ; the 

 third cirrus only fourteen in both rami ; and the sixth cirrus twenty- 

 six segments in both rami. Whereas in every specimen of T. porosa, 

 the longer ramus of the third cirrus contained more segments than 

 either ramus of the second. About half the segments, namely, those 

 in the middle of both rami of the third cirrus, are furnished with 

 coarsely and doubly pectinated spines, like those in T. porosa. 



Affinities. — Upon the whole, this species is more nearly allied to T. 

 porosa than to any other. In the cavity formed by the union of the ad- 

 ductor and articular ridges, it is allied to T. cosrulescens. This species 

 differs from all, in its little specific gravity, consequent on the parietal 

 tubes being only slightly filled up, and in the peculiarly serrated, 

 narrow, approximate ridges on the external surface of the walls. The 

 character derived from the adductor ridge, just alluded to, is remark- 

 able. In the shape of the terga, in the absence of radii, and in the 

 structure of the body, this species approaches closely to T. porosa. 



3. Tetraclita rosea. PL 10, fig. 3 a — 3 d. 



Conia hose a.* Krauss. (!) Die Sudafrikanischen Mollusken, Tab. 6, 



fig. 28, 1848. 

 Balanus Ctjmingii. Chenu. Illust. Conch., Tab. 4, fig. 5. 



Shell dirty white, tinged tuith pink ; parietes formed by a 

 single row of large tubes : radii generally narrow : tergum 

 with the spur rather short and broad. 



Hub. — New South Wales, Moreton Bay in lat. 27°, Port Jackson, and 

 Twofold Bay ; South Africa, Algoa Bay. Attached, in Australia, to littoral 

 rocks and shells ; often associated with T. purpurascens, Chthamalus antennatus, 

 and Catophragmus polymerus ; Mus. Brit., Cuming, Krauss, Darwin, Stutchbury. 



General Appearance.- — Shell steeply conical, often rather convex ; 

 dirty or brownish white, feebly tinted with pink; external surface 

 generally much disintegrated, and having in the upper part a pillared 

 appearance, owing to the exposure of the upfilled, large, square, parietal 



* I am greatly indebted to Professor Krauss for having sent me, for exami- 

 nation, the unique specimen collected by himself in Algoa Bay. There can be 

 no doubt of the identity of the African and Australian specimens. It is a singular 

 circumstance that the same species should occur in these two distant places, 

 and, as far as at present known, not in the intermediate, more tropical coasts. 



