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MOLLUSC A. 
Body sometimes naked, either destitute of any solid internal parts, or inclosing a shell or 
other hard substance, and sometimes provided externally with a shell covering or sheath- 
ing, but is never composed of tic o opposite valves united by a hinge. 
T HIS Class is divided into Five Orders, viz. Pteropoda, Gasteropoda, Trachelipoda, 
Cephalopoda, and Heteropoda. 
ORDER I. 
PTEROPODA. __6 Genera. 
Some only are furnished with a thin, cartilaginous or corneous shell. 
Hyal^ea. — Shell corneous, transparent, ovate-globose ; tridentated posteriorly ; open at 
the summit, and at the two posterior sides. 
Plate XIII. Fig. 7. H. tridentata. (Monoculus telemus? — Linn.) 
Clio. — This genus has no shell. 
Cleodora. — Shell gelatinous, cartilaginous, transparent, in shape of a reversed pyramid, 
or lanceolate, truncated and open at the summit. 
Plate XIII. Fig. 8. C. pyramidata. (Clio pyramidata. — Linn.) 
Limacina. — Shell thin, fragile, papyraceous, spiral ; the whorls re-united in a discoidal 
manner, like the Planorbis. 
Plate XIII. Fig. 9. (a) L. lielicialis. (Clio helicina.— Gmel.) [British Museum.] 
Cymbulia. — Shell gelatinous, cartilaginous, very transparent, crystalline, oblong, in shape 
of a shoe, truncated at the summit ; aperture lateral and anterior. 
Plate XIII. Fig. 10. C. Peronii. [Icon. Encyc. Method, pi. 464. fig. 4 &.] 
Pneumodermon. — This genus has no shell. 
