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ORDER IJ.__GASTEROPODA. 
Some are naked, others have a dorsal shell, not enveloping: again, others have a shell more or less 
hidden in their mantle. 
THIS Order is divided into two Sections Hydrobranchiz and Pneumobranchiz. 
SECTION I._-HYDROBRANCHI. 
Conratns Six Families, viz. Tritoniana, Phyllidiana, Semi Phyllidiana, Calyptraciana, 
Bulleana, and Aplysiana. 
TRITONIANA. —6 Genera. 
Without shells, either external or internal. 
Gravucus.—No shell. 
Eouts.—Ditto. 
Tritonia.—Ditto. 
ScyLizA.— Ditto. 
Tertruys.—Ditto. 
Doris.—Ditto. 
PHYLLIDIANA. —4 Genera. 
Some are mithout shells, either internal or external: others are wholly or partly covered by a shell, 
sometimes composed of one single piece, sometimes of a range of moveable and distinct pieces. 
Puytiip1A.—Has no shell. 
CuiTonELLus.—Body elongated, rather narrow, like a caterpillar, the middle of the back 
furnished with a multivalve shell; valves alternate, mostly longitudinal; they are 
nearly connected by their extremities. 
Plate XIII. Fig. 11. C. striatus. [Mrs. Mawe’s Cabinet.] 
Cutton.—Body oval-oblong, convex, rounded at the extremities; bordered all round by 
a coriaceous skin; partly covered by a longitudinal series of testaceous, imbri- 
cated, transverse, moveable pieces, set in the borders of the mantle. 
Plate XIII. Fig. 12. C. Magellanicus. (Idem.—Gmel.) 
Pate.ia.—Shell univalve, not spiral, covering the animal, shield-like, or retuse-conical; 
concave and simple below, without any fissure on the margin; the summit entire, 
and inclined anteriorly. 
Plate XIII. Fig. 13. P. miniata. (P. sanguinolenta—Gmel.) 
(a) Inside of ditto 
SEMI-PHYLLIDIANA. —2 Genera. 
PLEUROBRANCHUS.—Shell internal, dorsal, thin, flattened, often oblique-oval. 
Plate XIII. Fig. 14, 14 (a). P. plumula, (Bulla plumula.—Montagu.) 
E 
