432 SUPPLEMENT 
hooked themselves more firmly to the rocks when it was at- 
tempted to pluck them away; and the difficulty thus ex- 
perienced, has served Aristophanes as a comparison to express 
that of detaching an old woman from a young man, with 
whom she is in love. The balani serve as food in many 
places. 
We shall conclude by briefly noticing a few of the principal 
species, just premising, that they constitute subgenera in the 
text, and will be found named in the notes. 
The lepas balanus has a conical shell, with six valves, 
furrowed longitudinally, and marked transversely with fine 
strie. The operculum terminates in a curved point. It is of 
a yellow colour, the valves of a pale rose, and the furrows 
whitish. These last are united by teeth, which are fastened 
one in the other; and a similar mode of articulation unites 
them to the base, which is very thick, and pierced with 
several ranks of quadrangular cells, which communicate to- 
gether. Some canals hollowed longitudinally on the internal 
face of the valves abound with the most superficial of the 
cells which surround the base. This remarkable structure, 
which is far from being the same in all the species, has been 
described with much detail by Poli. The animal presents no 
particularity. It lives in numerous groups, fixed to rocks, to 
shells, and other marine bodies, in the Mediterranean and 
the Atlantic, on the coasts of England, Holland, and Green- 
land. 
The lepas balanoides has a truncated shell, with six smooth 
valves, rose-colour, marked in their length with purple lines. 
This species is more rare, says Poli, in the Mediterranean, 
than the preceding. Fabricius has found it much more fre- 
quently on the coasts of Greenland. It is also to be found on — 
our coasts, and those of Holland, united in groups intermixed 
with those of the preceding species. 
The lepas tintinnabulum has a shell with six valves, rose 
