THE SESSILE BARNACLES. 191 



hairs. The mandible has three strong conic teeth and a short fourth 

 one, the fifth tooth very Ioay and obtuse, nnited with the lower point. 



The maxilla is notched below the upper spines. Margin advancing 

 below the notch, bearing about 8 spines, the lower two larger. Lower 

 angle and upper margin are profusely hairy. 



The cirri are nearly black. First three of nearly equal length, 

 not half as long as the following three. Posterior ramus of cirrus i, 

 of 17 segments, about three-fourths as long as the anterior, of 21, 

 and having extremely protuberant segments. Eami of cirrus ii 

 subeqnal, of about 15 rather strongly protuberant segments. Cirrus 

 iii having nearly equal rami of about 15 segments; both rami very 

 denseh^ hairy. Cirrus vi has about 10 segments, the median ones 

 bearing 7 pairs of spines (fig. 59). 



Penis is nearly as long as cirrus vi, sparsely hairy near the end. 



The young of about 5 or mm. diameter are beautiful, starlike 

 barnacles, with two or three ribs on the carina, one on the carino- 

 Jateral, and three or four on the lateral and rostral compartments. 

 The number of ribs soon increases by intercalation in the intervals. 

 The pores of the parietes are much less numerous in young than in 

 old individuals, but they are already somewhat subdivided and 

 irregular at the 5 mm. stage. I have seen old specimens from a nar- 

 row support in which the membranous basis is reduced to very small 

 area, and the pores are closed at the basal edge. 



Bolamis ccmosvs has a superficial resemblance to Tetraclita due 

 to its membranous basis and porous wall. It is related to B. hala- 

 noides, but not closely, as the opercular valves are very different. 

 Darwin has called attention to points of resemblance (not, I think, 

 relationship) between the present species B. fioscidvs and B. nuhilis, 

 but there are also important differences; altogether it is an isolated 

 species. 



B. cariosus is a shallow- water and shore species, commonly grow- 

 ing on pebbles, shells, such as living MytUm^ Pecten^ and other cast- 

 up shells. The single example from a deep-water station {Albatross 

 station 2871) has evidently been dead a long time and probably 

 drifted into deep water from the shore. All of the rest of the series 

 was taken by collectors from the shore. 



Plate 46, figures 1, 2, 2-7, 4, G, 8, are from Unalaska specimens; 

 figures 3 and 7 are from Nazan Bay, Atka ; figure 5 from Neah Bay, 

 Washington. Figures 1 and 8 are slightly enlarged, the others 

 natural size. 



Ivarely B. cariosvs grows on sponges which almost bury the bar- 

 nacle. The group shown partly cleared of the sponge in plate 4G, 

 figure 0, is from Sanborn Harbor, Nagai Island, Shumagins. The 

 parietes are narrow, radii wide in the lower part, narrow above, the 

 ahe forming the greater part of the walls between the parietes. The 



