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Sepia (Cuttlefish). Body o\al, with narrow 

 lateral fins. Eight short and two long 

 " arms," each with four rows of suckers. 

 Two gills. The shell internal (" cuttle- 

 bone "). An ink-sac. 



Nautilus. The front part of the " foot " 

 formed into lobes with tentacles instead 

 of suckers. Four gills. An external 

 piano-spiral and chambered shell ; the 

 last or outer chamber containing the 

 body. 



Helix pomatia (The Edible Snail). 

 A Type of the Gasteropoda. 



Describe the External Features of the Snail. 



The body consists of head, "foot" and visceral hump. 

 The elongated muscular "foot" is the flattened ventral 

 portion of the body- wall. Overlying the "foot" is the 

 head region which bears anteriorly two pairs of retractile 

 " horns " or tentacles ; on the tips of the upper and longer 

 pair are the eyes. The mouth is between the front of the 

 " foot " and the under surface of the head. The genital 

 aperture is situated below the right large tentacle and at 

 the end of the groove along the right side of the body. 



The head and " foot " may be withdrawn within the 

 shell, a right-handed conical spiral, which is carried some- 

 what obliquely on the back, and within which is lodged 

 the twisted dorsal visceral hump containing the principal 

 internal organs. The integument of the hump is thin ; 

 a free fold of it, the mantle, extends over the back and 

 ends in a thickened edge, the collar, around the mouth of 

 the shell. This collar is fused with the body-wall, except 

 at an opening on the right side, the pulmonary aperture. 

 Beside the pulmonary aperture there is a smaller opening, 

 the anus. 



How does the Snail Move ? 



In the "foot" there is a tubular pedal gland, which 

 opens below the mouth and which secretes slime. By 

 means of this slime, and by wave-like contractions of the 



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