(sect, f), balanus inclusus. 301 



gated in the rostro-carinal axis, sometimes to a great degree; I have 

 seen a specimen '25 of an inch in this axis and only '1 in its broadest 

 part; but this is a very unusual degree of elongation. The most 

 remarkable character is the extraordinary narrowness of the carina, the 

 carino-lateral compartments, and of the rostrum, compared with the 

 great breadth, especially along the basal margin (PI. 8, fig. 10 5, 10 c), 

 of the lateral compartments. The radii are of unusual breadth. The 

 tips of the rostrum and of the lateral compartments are a little arched 

 in, tending to make the shell somewhat globular. The true basis is 

 extremely narrow (fig. 10c): it is deeply grooved, from clasping the 

 thin, cylindrical stem of the coral to which it had adhered; and I have 

 seen specimens in which the opposite edges of the groove had met, a 

 tube having been thus actually formed. From the grooved basis, and 

 from the elongation of the shell in the rostro-carinal axis, this species 

 presents so close a general resemblance to Balanus calceolus, and its 

 allies, that I have seen it in a collection arranged on the same tablet 

 with a fossil specimen of B. calceolus. Notwithstanding the above 

 several strongly-marked characters, by which this variety differs from 

 the ordinary form, there is a resemblance in colour and aspect, which 

 though difficult to be described, made me from the first suspect that the 

 two were specifically identical. In no point of real structure is there 

 any difference, excepting that, perhaps, the pores in the basis are here 

 rather smaller ; but this might arise from the little development of the 

 peculiar basis. Having come to this conclusion, I was interested by 

 finding a specimen in Mr. Wood's collection, which had originally 

 fixed itself (judging from the form of the basis) on a cylindrical stem, 

 but which had subsequently grown on to an adjoining flat surface ; 

 consequently, one side of the shell presented all the peculiar characters 

 of the present variety, whereas the other side, at the rostral end, was 

 undistinguishable from the ordinary form. The unequal development 

 of the rostrum on the two sides was very striking, and clearly showed 

 how great an effect could be produced by the nature of the surface of 

 attachment. 



This singular variety cannot be considered accidental, in the sense in 

 which this term may be applied to some varieties : the larva evidently 

 fixes itself intentionally, in a certain definite position, on the branch of 

 the coral (when a branch is chosen), exactly as in the case of Balanus 

 calceolus, or Scalpellum vulgare. But when other species of Balani 

 occasionally fix themselves on branched corals, their position seems to 

 be accidental and unsymmetrical ; thus among the symmetrically elon- 

 gated specimens of the present species, I found one specimen of Balanus 

 bisulcatus, which had evidently been attached in an almost transverse 

 position to a branch, and had thus become much distorted ; so, again, 

 I have seen specimens of the recent B. amaryllis attached irregularly 

 to a Gorgonia, in the midst of the symmetrically elongated shells of 

 Balanus navicula, an ally of B. calceolus. 



This variety does not seem to attain so large a size as the ordinary 

 form. 



Affinities. — This species is allied to the two last-described fossils, 

 namely, B. varians and unguiformis, but is perhaps more nearly related 



