REPORT ON THE CIRRIPEDIA. 165 



The specimens have irregularly folded walls, with the surface corroded and entirely covered 

 by the calcareous coating of the Balanus; they are so totally embedded in this calcareous 

 layer, that their surfaces only appear when the lime is removed. The orifice of the 

 shell, with the indistinctly visible opercular valves, betrays the presence of this Cirriped. 

 The opercular valves also have the surface corroded and disintegrated; having been 

 isolated and cleansed as far as possible (boiled with caustic potash, &c.) it is possible to 

 judge of their form; in general it is much the same as described by Darwin. The tergum 

 not only corresponds to the specimens of Darwin because of the very prominent articular 

 ridge, but also because of the arched and protuberant carina! margin. 



This species inhabits the coast of south Africa and Natal, of west Africa, Luanda, 

 and the Gold Coast. The Cape Verde Islands must now be added as a new locality. 

 Darwin saw a specimen from the West Indies, but it was the variety which so common lv 

 adheres to ships' bottoms. 



July 1873, 7 to 20 fathoms; St. Vincent Harbour, Cape Verde Islands. 



Chtharnalus challengeri, n. sp. (PI. XIII. figs. 35-38). 



Shell white, thin, brittle; surface smooth, irregularly folded; sutures between the 

 valves distinct. Tergum with an arched and protuberant carina! margin, elongate in the 

 direction of the spur. 



I propose this new name for a species of the genus Chthamalus of small size, which 

 was taken from the screw of H.M.S. Challenger. There is a considerable number of 

 specimens, the greater part of which have an irregular cylindrical shape. I think they are 

 all of the same age, and as some of them are furnished with eggs, they are probably 

 quite or at least very nearly full-grown. The cylindrical specimens form, as a rule, 

 groups, being attached to one another by then." lateral compartments. The other 

 specimens have a flattened conical shape ; they are either isolated or associated in 

 groups; in the latter case, however, they adhere to one another only by the basal 

 edges of their compartments. Often, but most obviously so in the cylindrical specimens. 

 the basal margin is continued into a ledge, which, however, is not inflected inwards 

 but outwards. In the flat-conical specimens the surface of the parietes is almost totally 

 smooth, and in them folds are only visible near the basal margin ; hence in these speci- 

 mens the basal edge is sinuous. The cylindrical specimens distinctly show that they 

 were in the beginning flat-conical, like the other specimens. The cylindrical lower part of 

 the shell is often narrower than the upper part. In these specimens the walls are almost 

 flat in the lower half, but irregularly folded in the upper half. The radii in all the speci- 

 mens are very narrow, their sutural edges are not at all crenated ; the ake are broad, 

 their upper edges are only slightly oblique. In all the specimens the sutures are 

 distinctly visible. 



