432 BALANID.E. 



General Appearance. — Shell elongated, sub-cylindrical, with the 

 upper end rather wider than the lower, and therefore widening in a 

 direction the reverse of that usual with sessile-cirripedes. The shell is 

 often a little bent to one or the other side : it is surrounded by from 

 two or three to about ten very prominent, strong, blunt ridges or belts, 

 placed at rather irregular distances from each other. The surface is 

 finely striated longitudinally. The six compartments are of nearly 

 equal sizes and shapes. In full-grown specimens the parietes are not 

 wider at the base, and often they are even a little narrower, than at 

 the summit of the shell : in young specimens the parietes do widen a 

 little downwards. The radii are narrow ; but in young specimens 

 they are proportionably much broader (PI. 17, fig. 3 6) than in old 

 specimens. The whole compartment, including the radius and wall, 

 is always a little wider at the summit than at the base, in accordance 

 with the shape of the whole shell. The operculum consists of four 

 nearly equal-sized, similar valves, projecting above the upper end of 

 the shell, which is always broken and jagged : the valves are united to 

 the sheath by a very thick, much folded membrane. The aperture leading 

 into the sack is bordered by very prominent lips, projecting above the 

 opercular valves ; the latter have their upper layers always scaled off. 

 The shell is imbedded in the whale's skin up to the level of its oper- 

 culum. The largest specimen which I have seen was barely one inch 

 (*95) in diameter at the summit, and 1*5 in length ; the longest speci- 

 men which I have seen scarcely attained a length of one inch and three 

 quarters. 



Structure of the Shell. — The parietes are thin, and if the sheath 

 (which extends to near the basis) be removed, they are rendered ex- 

 tremely thin. They are formed by an outer and inner lamina, united 

 by fine longitudinal septa, projecting at the basis beyond the laminae. 

 The pores thus produced (which in a transverse section are oblong in 

 outline), run up to the summit of the shell, and are not filled up by 

 shelly matter ; but I presume that the included tubular threads of 

 corium are protected, at the broken upper end of the shell, by trans- 

 verse membranous septa. The outer lamina of shell, as in Coronula, 

 is formed, though obscurely, by the union of ledges projecting from 

 the longitudinal septa. The circular prominent belts, surrounding the 

 shell, are formed by the longitudinal septa, at certain, irregular and 

 rather distant periods, growing outwards ; the wall at each belt being 

 increased to nearly twice its thickness in other parts. At each belt the 

 threads of corium within the parietal pores send off minute branches 

 to supply the thickened wall. These belts, which continuously sur- 

 round the shell, correspond (as is best seen in young specimens), with 

 the little knobs or beads, which, in Coronula (PI. 16, fig. 4), rise 

 separately, and not quite regularly, on the longitudinal parietal septa, 

 and which, I believe, are formed at every successive period of growth ; 

 here they are much larger, stand in straight transverse rows, become 

 confluent, and are formed only at occasional intervals. The whole 

 external surface of the shell is covered by membrane, stronger and more 

 persistent than is usual with most cirripedes. 



Internally the sheath extends almost to the basis of the much elon- 



