- BALANUS, 13 
Scutum and tergum articulated together, sub-triangular; compartments six; basis 
calcareous or membranous. 
The genus Balanus already includes 45 species, recent and fossil, and consequently 
in my volume published by the Ray Society, I have divided the genus into sections, 
on characters derived from the porosity of the parietes, radii, and basis; and on whether 
the basis be membranous or calcareous. But as here we have to describe or notice only 
eleven species, I have thought it more convenient to drop the sections, and in their place 
add a few words to each of the diagnostic characters. The genus is quite distinct from 
all the other genera of Sessile Cirripedes, with the exception of the sub-genus Acasta, 
from which its separation, it must be confessed, is in one sense artificial; for the 
species of this sub-genus graduate into those of Balanus (such as B. calceolus and its allies), 
which have their shells elongated in the rostro-carinal axis, and which live attached to 
Gorgoniz. These latter species have been generically separated by some authors from 
true Balanus; but I have found it impossible to effect this; and even the section of the 
genus, including these species, is hardly distinct enough from the adjoining sections. 
On the other hand, the sub-genus Acasta, in another sense, is a very natural one, inas- 
much as all its species are closely allied together in essential structure, in general 
appearance, and in habit; and as the genus Balanus is already large, I have thought 
it best to adopt Acasta, which has been already admitted by many authors as a sub-genus. 
I need only further remark, that from reasons already assigned, I have thought it useless 
to give in this work long generic descriptions. 
1, BALANUS TINTINNABULUM. ‘Tab. I, fig. la—t1d. 
LEPAS TINTINNABULUM. Linn. Syst. Nature, 1767. 
— — Ellis. Phil. Transact, vol. 50, 1758, Tab. 34, figs. 8 and 9. 
— — Chemnitz. Neues. Syst. Conch., 8 B. (1785), Tab. 97, 
figs. 828-831. 
BaLANUS TULIPA. Bruguiére. Encyclop. Meth., 1789; sed non B. tulipa alba, in 
Chemnitz ; nec non B, tulipa, O. F. Miller, Zoolog. Dan. ; nec 
non B. tulipa, Poli, Test. ut Sicilice. 
— — G. B. Sowerby. Genera of Recent and Fossil Shells, Tab. Genus 
Balanus. 
LePAs CRISPATA (var.) Schroter. Finleitung Conch., vol. iii, Tab. 9, fig. 21. 
— spinosa (var.) Gmelin. Linn. Syst. Nat. 
— TINTINNABULUM, SPINOSA, CRISPATA BT PORCATA. W. Wood. General Con- 
chology, 1815, Pl. 6, figs. 1,2. Pl. 7, figs. 4,5. Pl. 8, figs. 1—5. 
BaLANUS TINTINNABULUM. Chenu. Illust. Conch. 
a D’OxBIeNII (var.) Chenu. Illust. Conch., Tab. 6, fig. 10, sed non Tab. 4, 
fig. 13. 
— crassus. Sowerby (!) Min. Conch., 1818, Tab. 84. 
