74 Lamarck’s Genera of Shells. 
First Order. 
SEssILE CirRIPEDA. 
Body without pedicles, enclosed in a shell, fixed immediately 
on marine substances. The mouth in the upper anterior part 
of the body. 
There is a great difference in the shells of the sessile and the 
pedunculated cirripeda; the former are never compressed at 
the sides, generally appear to be formed of a single piece, 
like a cone, or tube truncated at the summit, and always have 
an operculum, composed of two or four moveable pieces, in 
their interior. The shell and its operculum are solid and cal- 
careous. ‘The shell of the pedunculated cirripeda, on the con- 
trary, is always multivalve, and, in most of them, consists of 
five unequal pieces, forming, when not open, a cone laterally 
compressed. Some species have, besides, several small acces- 
sory pieces. Linneus included both the orders in one genus, 
under the name of lepas, which Bruguiére divided into two 
genera, balanus and anatzfa. These genera answer to our two 
orders. 
The first order contains six genera*. 
1. Tubicinellat. 
Body enclosed in a shell, on the upper part protrude small 
setaceous, cirrous, and unequal arms. Shell univalve, opercu- 
culated, tubular, straight, rather attenuated towards the base, 
with annular transverse ribs ; truncated at both ends, open at 
the summit, and closed at the base by a membrane. Opercu- 
lum with four obtuse valves. 
Type.  Tubicinella balenarum}, adheres to the whales of 
the seas of South America. PI. iii. Fig. 9. 
* Dr. Leach has given a short, but comprehensive, article in the Supple- 
ment to the Encyclopedia Britannica, on the Cirripeda. He divides them 
into two orders; 1. Campylosomata, from xapavacy and copa, meaning 
a flexible body ; and, 2. Acamptosomata, from axel and cw, an inflex- 
ible body. The first order contains five genera, viz., Otion, Cineras, Pentelas- 
mis, Scalpellum, Pollicipes. The second order contains nine genera, viz., 
Tubicinella, Coronula, Chelonobia, Pyrgoma, Creusia, Acasta, Balanus, 
Conia,and Clisia—See Ency. Brit. Sup, Art. CirR1PEDES. 
+ From éubicen—a trumpeter. ¢ Balena, a whale. 
