16 INTRODUCTIOISr. 



back, and surrounded by a fringe ; feelers, two or four, 

 seated on the upper part of the body in front, and retractile 

 within their proper receptacles. 



3. Spio. — Body projecting from a tube, jointed and fur- 

 nished with dorsal fibres ; peduncles, or feet, rough with 

 bristles and placed towards the back; feelers two, long, 

 simple ; eyes two, oblong. 



4. Amphitrite. — Body projecting from a tube and an- 

 nulate; peduncles, or feet, small, numerous; feelers two, 

 approximate, feathered ; no eyes. 



5. Terebella — Body oblong, creeping, naked, often 

 enclosed in a tube, furnished with lateral fascicles or tufts, 

 and branchicfi ; mouth placed before, furnished with lips 

 without teeth, and protruding a clavate proboscis ; feelers 

 numerous, ciliate, capillary, seated round the mouth. 



6. Nereis. — Body long, creeping, with numerous lateral 

 peduncles or feet, on each side ; feelers simple, rarely 

 wanting; eyes two or four, rarely none. 



7- AsciDiA. — Body fixed, roundish, and apparently issuing 

 from a sheath ; apertures two, genei'ally placed near the 

 upper end, one beneath the other. 



8. Tethys Body detached, rather oblong, fleshy, with- 

 out peduncles; mouth with a terminal cylindrical proboscis, 

 under an expanded membrane or lip; apertures two, on the 

 left side of the neck. 



9. Triton. — Body oblong; mouth with an involute spiral 

 proboscis ; tentacula or arms, twelve, six on each side, 

 divided nearly to the base, the hind-ones cheliferous, 



10. Sepia Body fleshy, receiving the breast in a sheath, 



with a tubular aperture at its base; arms eight, beset with 

 numerous warts or suckers, and in most species two pedun- 

 culated tentacula; head short ; eyes large; m.oiith resembling 

 a Parrot's beak. 



It is exclusively upon the shape of the shell, and not upon 

 the structure of the animal inhabitant, that the Linna^in 

 arrangement of Conchology is founded. 



In early periods, naturalists were in much doubt whether 

 to found their Conchological arrangements on the animal, 



