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b. Balanus tintinnabulum, var. costatus nov. var. Pl. XIV, fig. 5 and 6. 
This form is represented by a fine specimen with very prominent ribs, the basal extre- 
mities of which extend beyond the elongated, rounded circumference of the basis. I do not 
know, of course, whether its shape would undergo changes during growth, and if so, what changes 
they would be — for the present I think it best to describe it as a distinct variety. 
The shell has a very regular shape, flatly conical, with a large rhombiform orifice and 
triangular radii, the upper margin of which runs nearly parallel to the basis. The surface is 
distinctly ribbed, much stronger ribs alternating with groups of smaller and narrower ones. 
The radii are feebly striated in horizontal direction, the striae representing the very delicate 
canals which traverse them. The parietes as well as the basis have distinct pores. The outer 
surface of the ribs is white, the furrows between them being coloured pink or red, with here 
and there small spots coloured darker red. The greatest diameter of the basis is nearly 14 mm., 
the shortest not quite 10 mm. 
The scutum (PI. XIV, fig. 6¢ and c) has the broad and reflexed articular ridge like the 
other forms of this species, and the tergum looks very much like that of a typical B. tén- 
tennabulum, its furrow being open, however, as is usual in young specimens. The spur is 
broad and flat, and cannot be said to be distinctly produced at the internal surface of the 
valve (Pl. XIV, fig. 6a and d): differences which, probably, will change when the animal 
grows older. 
c. B. tintinnabulum, var. plicatus nov. var. Pl. XIV, fig. 7. 
Two specimens of this new variety were collected along with the foregoing. They are, 
probably, young specimens. The smaller is attached to the larger and, perhaps, slightly 
older one. 
The shape is conical, but the circumference of the basis is smaller, that of the orifice 
relatively larger, the whole shell, in consequence, more steep than the case is with the var. 
costatus. Corresponding ribs are present, but the stronger ones are by no means so promi- 
nent; their basal extremities hardly extend beyond the circumference of the basis. So this 
circumference is neatly circular, the extremities of the ribs forming small round festoons only 
round that circumference. The surface of the ribs, of the deeper furrows, and of the spots here 
and there along the margins of the valves, are coloured in the same way, though perhaps not 
quite so distinctly, as in the variety costatws. The size of the basis is about 10 mm. in diameter. 
The shape of the opercular valves generally corresponds to that of the var. costatus. 
Both forms have the lines of growth on the scutum more prominent, than, according to 
Darwin’s description, one might expect them; these lines of growth are slightly sinuous; 
their crests — especially those near the basal margin — are furnished moreover with a row 
of minute points, and consequently are slightly crenated. The tergum has the furrow open and 
relatively broad; the spur as a whole is, however, not quite so broad as in the variety 
costatus, its extremity is slightly more rounded. The crests for the tergal depressor muscle 
are, in this variety, not quite so strong as in the var. costatus. 
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