14 
pedicle; valves sometimes moveable and distant, 
sometimes soldered together, lined internally by the 
mantle. 
OrpDER SESSILIA. 
Affixed and not pedunculated : aperture superior and 
anterior. 
Genus CORONULA. 
Sessile, suborbicular, seemingly one entire piece, conoid 
or retuse conical, truncated at the extremities ; 
substance thick, hollowed interiorly by radiating 
cells : operculum with four obtuse valves. 
C. Diapema. Lam. 1.— Bl. t. 86. f. 4-—Lepas D, 
Lin.—Ch. f. 843.—IList. ¢. 445. f. 288.— Born. t. 1. 
f. 5. 6.—W ood, G. C. t. 4.—Da. Cos. t.7. f. 2.— 
Don. t. 56. f. 1. 2.—Turt. D. p. 75.—D. p. 24.-— 
Batanus. D. Mont. p. 13.—Brug. p. 171.—Sub- 
compressed, hemispheric, dirty white, with twelve com- 
partments, six depressed, flat, and striated transversely, 
the others, which are alternate, are prominent with four 
five or six elevated longitudinal ridges and transverse 
striee ; at the top is a deep cavity, funnel shaped, hex- 
agonal within, at the bottom of which is the aperture, 
the ribs are also furnished with divisions or cells in a 
radiated manner and lined with a coriaceous membrane, 
Diam. 2 to3. Rare, except in Scotland and its isles, 
