(SECT. F), BALANUS FLOSCULUS. 291 



PL 8, fig. 5 c, and others as much elongated as in fig. 5 d: these latter 

 come from an elongated cylindrical shell. The valve externally is 

 unusually convex : the apex, also, projects freely to an unusual degree. 

 Internally, the articular ridge is moderately prominent : the adductor 

 ridge is prominent and much curved : in the upper part it either lies 

 close to, or at some little distance from the articular ridge. The lateral 

 depressores are attached to several little crests, occupying a cavity, 

 (often bordered above by a little ridge) close beneath the adductor 

 ridge. Tergum> extraordinarily narrow and elongated ; beak trian- 

 gular, purple : a longitudinal furrow runs down the valve : spur nar- 

 row, long, bluntly pointed, lying close to the basi-scutal angle of the 

 valve : the scutal margin is nearly straight and parallel to the spur. 

 Internally, the articular ridge is prominent : the crests for the depres- 

 sores are moderately well developed : the upper part of the valve is 

 marked by a purple patch, bounded on one side by the articular ridge, 

 and on the other side by a very slight special ridge. There is some 

 variability in the narrowness of the whole valve, and in the sharpness of 

 the spur. 



Parietes. — The under surface, in the more depressed varieties, is 

 roughened in a remarkable manner nearly or quite up to the sheath, 

 with very irregular, projecting, and branching ridges, and sometimes 

 with depending points. These ridges and points are granulated on 

 their under surfaces. The roughened surface in the more conical varie- 

 ties is confined to the basal inner margin. This structure is nearly the 

 same as that in B. imperator, represented (PI. 8, fig. 4 c), but the little 

 ridges are here more apt to be concentric, instead of radiating. The 

 lateral edges of the compartments on the inside, especially the carinal 

 edges, project inwards beyond the inner surface of the shell. The sheath 

 is but little hollow on its under side. The diametric growth of the shell 

 seems to be quite capricious ; in the same group, some individuals thus 

 increasing, and others not at all. When the radii are developed they are 

 narrow and white, with their upper margins nearly if not quite parallel 

 to the basis : their sutural edges are formed by large, irregular, branch- 

 ing teeth or septa. The alee, also, have their sutural edges coarsely 

 crenated ; and when the shell increases by diametric growth, they are 

 added to above the opercular membrane, so as to be nearly square at top. 



Basis. — When a shell is removed from the surface of attachment, 

 and inspected even under a lens, there appears to be no basis whatever, 

 either adhering to the shell, or to the supporting surface : but when a 

 more careful examination is made, wkh a higher power, an excessively 

 thin, translucent, calcareous, irregular layer, or rather film, can almost 

 always be discovered. This would be more easily distinguished if the 

 specimens had adhered to rock instead of to the rugged shells of mol- 

 luscs. At one time I thought the basis was partially membranous, for 1 

 have certainly scraped off small fragments of membrane from the sup- 

 porting surface ; but these, when examined under the compound 

 microscope, seemed always to consist of a thin sheet of the yellow 

 cementing tissue; and in some instances, a brittle film of shell, repre- 

 senting the true basis of the cirripede, still adhered to the upper surface 

 of the membranous bits of cement. Nevertheless, so imperfect is the 



