410 Dr. F. Miiller on a Hybrid Balanus. 



in the middle between the carina and the rostrum ; the scuta 

 are always considerably narrower ; the rows of pits on the 

 outer surface are never wanting ; nor on the inner surface are 

 adductor ridges, traceable nearly to the basal margin, to be 

 seen ; the terga never have such narrow spurs, or a longitu- 

 dinal fiuTOw, or ridges for the muse, depressor projecting be- 

 yond the basal margin ; the strong curved teeth on the cirri of 

 the third pair and the strong tooth on the jDeduncle of the fifth 

 pair are never wanting ; there are never more than four pairs 

 of set£e on the posterior cirri, &c. 



In B. assimilis^ on the contrary (a species so common here 

 that every potsherd, shoe-sole, or rope's-end which has lain 

 for some time in the sea is covered with it), I have never seen 

 a similar reddish colour to that presented by one of the sup- 

 posed hybrids ; I always found the radii quite narrow, covered 

 with a thin membrane, never broad and shining ; I always 

 found short spines between the hairs of the opercular j^ieces, 

 and the spur narrower, the labrum always beset with nume- 

 rous teeth ; and in the animals which I have to-day examined 

 for this purpose, but which, indeed, are not very numerous, I 

 found constantly six jDairs of set£e upon some joints of the 

 posterior cirri, not to mention other small distinctions. 



It is evident that the differences from either species are too 

 considerable for a mere variety ; they would be of sufficient 

 importance to lead us to regard our animal as a distinct spe- 

 cies, if there were not other considerations opposed to this 

 view. Species of Balani, where once they occur, do not usu- 

 ally appear so isolatedly that in the course of a month only 

 four specimens can be brought together*. And how sm'prising 

 would it be that upon the stem of Caryoa a third species 

 should be domiciled amongst B. armatus and assimilis, stand- 

 ing in so peculiar a manner in the middle between the two 

 species as do our animals, which agree with B. armatus in 

 almost everything by which they differ from B. assimilis (in 

 the coloration of one of the shells, in the firm union of their 

 pieces, in the structure of the shining striated radii, in the 

 structure of the labrum), and which in almost everything by 

 which they differ from B. armatus (in the formation of the 

 walls, the aperture, the opercular pieces, &c.) agree with B. 

 assimilisj and, again, in other respects (as in the number of 



* I cannot say exactly among what number of B. armatus the four 

 hybrids were found, as I have used up a great quantity of the former 

 without coimting them ; the number may be about 400. For a month or 

 more I have daily dived upon the Carijoa rock whenever the sea was 

 sufficiently quiet, and not unfrequently obtained from thirty to forty 

 Balani at once upon the polypes brought up. 



