46S BALANlDiE. 



Month. — The labrum is strongly toothed : the palpi have long hairs 

 along the exterior basal margin : the mandibles have only three main 

 teeth, and the inferior coarsely pectinated portion is short ; the max- 

 illae are deeply notched. Cirri: the first and second pairs have their 

 rami slightly unequal in length; the third pair differs from the same pair 

 in the other species of the genus, in having some few of the basal seg- 

 ments on the anterior ramus thickly clothed with spines, so as to be 

 brush-like : there is even a trace of a similar structure in the lowest 

 segments of the posterior ramus. In the three posterior pairs of cirri 

 the segments are much elongated, and support four pairs of spines. 



BranchicE. — Unknown . 



8. Chthamalus scabrosus. PI. 19, fig. 2 a — 2d. 



Shell [when well preserved) dull purplish-brown : sutures 

 formed by oblique interfolding lamina, though rarely well 

 developed : tergum with a deep narrow pit, at the basi-carinal 

 angle, for the depressor muscle. 



Ilab. — Peru, Chile, Chiloe, Tierra del Fuego, Falkland Islands. Very 

 common; attached to littoral rocks and shells, and often associated with 

 Balanus flosculus, and sometimes with Chthamalus cir rat us ; Mus. Brit., Cuming, 

 W. Dunker, Darwin. 



General Appearance and Structure. — Shell generally depressed ; 

 when growing crowded, sometimes cylindrical : colour dingy purplish- 

 brown, but when much corroded, dirty gray ; very young shells are very 

 dark green, owing to the corium, which is of this colour, being seen 

 through the valves. Surface generally rugged, from irregular slight 

 longitudinal folds, and from the transverse overlapping tile-like 

 lines of growth ; but sometimes the surface is nearly smooth, with 

 very slight longitudinal folds, these being gray coloured, the inter- 

 mediate parts being pale dingy purple, the shell thus becoming 

 striped. Orifice rhomboidal, passing into trigonal, owing to the 

 great width of the carinal end. Sutures generally very distinct, 

 rarely obliterated in the cylindrical varieties. Radii narrow, 

 generally exposing much of the alae, which are plainly marked by lines 

 of growth : the radii themselves, when well developed, which is not 

 often the case, consist of small laminae or ridges, placed on both sides 

 of the sutures, and interfolded or interlocked together: usually only a 

 trace of this structure is exhibited, but occasionally, along some or 

 along all the sutures (as in the specimen figured), the laminae of the radii 

 interfold, as plainly as in C. intertextus. The alse differ slightly from 

 the alee of the other species, in not forming so much of a rectangular 

 projection, the lower margin running with a gentle curve into the 

 parietes. The internal surface of the parietes is either smooth, or 

 near the basal margin is roughened with depending points: in some 



