Lamarck’s Genera of Shells. 75 
2. Coronula*. 
Body sessile, enclosed in a shell, protruding small setaceous, 
cirrous arms, from the upper part. Shell sessile, apparently 
univalve ; suborbicular, conoidal, or blunt conical ; truncated 
at the extremities; sides very thick, hollowed into radiating 
cells. Operculum quadrivalve; valves obtuse. No annular 
transverse ribs. 
Type. Coronula diadema TF. 
Shell ventricose, cylindrical, truncated; hexagonal, quadri- 
costate ; ribs longitudinal, transversely striated. Pl. iii. Fig. 10. 
3 Species. 
Adhere to whales, tortorses, §c. 
3. Balanusf. 
Body sessile, enclosed in an operculated shell. Two rows 
of numerous, unequal, fringed arms, each composed of two 
cirri, supported on a pedicle, and extending beyond the oper- 
culum. Mouth not prominent; four transverse jaws, toothed, 
and besides four hairy palpiform appendages. 
Shell sessile, fixed, conical, apex truncated; closed at 
the bottom by an adhering testaceous lamina. Aperture 
subtriangular, or elliptical. Operculum interior, quadrivalve ; 
valves moveable, inserted near the inner base of the shells. 
Type. Balanus sulcatus §. . 
Shell whitish, conical, longitudinally furrowed; furrows 
obtuse ; ribs transversely striated. 
Pl. iii. Fig. 11. 29 Species. 
4, Acasta. 
Animal 2... 4: »-\ 
Shell sessile, oval, subconical, composed of separable pieces. 
Cone formed of six lateral valves, unequal, united ; at the bot- 
tom an orbicular lamina, concave on the inner side, resembling 
a little deep dish, or cup. Operculum quadrivalve. This shell 
* From corona, a crown. + Diadem. t An acorn. 
§ Furrowed, Lamarck has given the balanus angulosus as the type of 
this genus, but no reference to any plate, or synonym, We have therefore 
thought it better to give the description and figure of the second species, 
balanus sulcatus. According to Lamarck, the two are nearly allied. 
