272 balanidjE. 



the tidal limits round the shores of Great Britain, and apparently of 

 the northern United States. Besides numerous specimens sent to me 

 from very many English localities, the late Mr. W. Thompson, of 

 Belfast, kindly placed in my hands his very large collection ; from these 

 materials it appears that B. balanoides is the only tidal species in the 

 northern parts of our island ; but in the south and south-west, it is 

 associated with the Chthamalus stellatus and Balanus perforatum. I 

 doubt whether this species ever lives below the lowest tides ; the case 

 of a few specimens being mingled with B. improvisus and crenatus, 

 (mentioned under the latter species,) at the bottom of a rudder of a small 

 vessel, about six feet deep, is hardly an exception, for the water would 

 there be troubled and aerated almost as in a breaker; and on this very 

 rudder the upper two or three feet were coated exclusively by the B. 

 balanoides. This species lives on rocks at both the uppermost and 

 lowest limit of the tides ; I am informed by Mr. Thompson, that he 

 has seen specimens attached to a spot not covered by water during 

 neap-tides. As a proof of its tenacity of life, Mr. Thompson informs 

 me that he accidentally kept some specimens in a box, in a warm sit- 

 ting-room, and found them alive seven days afterwards. This same 

 most accurate observer finds, however, that B. balanoides is very 

 susceptible to brackish water; he says, " that having kept some speci- 

 mens alive for a week in excellent health, the water being changed once 

 in thirty-six hours, they were one day killed instantly by some water, 

 though brought from the same part of the estuary as usual, having 

 been rendered brackish by much rain having lately fallen." I may 

 recall the fact, that B. improvisus lives daily for hours in absolutely 

 fresh running water. 



The B. balanoides lives attached, often continuously coating many 

 square feet of the surface, to rocks, pebbles, wooden-piers, littoral 

 shells and ulvae. The most northern point whence I have received 

 specimens, is in lat. 66° 34' in North America, collected by Mr. Suther- 

 land ; and the most southern point is Delaware Bay, in the United 

 States, in lat. 39° ; I do not believe that this species extends into the 

 Mediterranean, for Ranzani (Mem. di Storia Nat.), who particularly 

 attended to the nature of the basis, was not acquainted with any 

 Balanus having a membranous basis ; and Poli (Test. Ut. Sicilian,*) 

 describes only two species thus characterised, and these are manifestly 

 Chthamali. 



With respect to the rate of growth of this species, I am 

 indebted to Mr. W. Thompson for the following note : — 



" Sept. 29, 1848. — I examined a great number of Balani, in reference 

 to the growth made by them during the present season, and found it 

 to average three lines in diameter, and at most four lines. I saw 

 a few minute specimens, only one line in diameter, showing tbat the 

 species continued to breed until lately : these latter were probably not 

 more than four weeks old. The young of the present year are plainly 

 distinguished from the older ones, by their pure white colour and fresh 

 appearance. Judging from the size of this year's specimens, and of 



