< 63- ) 



C. Aquatic ; 2 tentacula. 



TVithout a shell, 



5. Onchidium. (1) ■ 

 chanan. 



A broad fleshy mantle. 2 Long retractile ten- Orifice of respiration 

 PI. 16, fig. 8. tacula, and two triangu- under the posterior part 



lar lips. of the mantle. 



JVith shells. 

 6. Ancylus. Geoff. 



Eyes at the inner base 

 of the tentacula. 



7. Planorbis. (2) Brug. 

 PI. 16, fig. 10. 



Tentacula thin, fili- Ditto, 

 form. 



7. Lymn/EUS. (3) Lam. 



Tentacula compress- Eyes near the base of 

 ed, broad, triangular. the inner edge. 



8. Physa. (4) Drop. 



Two dentated lobes to Tentacula thin, point- Eyes at the inner base, 

 the mantle. > ed. which is much enlarged. 



9. Auricula. Lam. 



10. Conovula. Lam. 



11. TORNATELLA. Lam. \ Animals unknown, but (from the form of the shell 



I and the absence of the operculum) approximating 



t \ to the Auricula. 



12. Pyramideila. Lam. J 



(1) The.mollusca, destitute of jaws, have a muscular gizzard, followed by two 

 membranous stomachs, 



(2) A red and abundant liquor exudes from the edges of its mantle, but it is not 

 their blood ; they are the constant companions of the Lymnseiin all stagnant waters. 



(3) We find them floating on the surface of the water with the foot turned up- 

 wards, and very rarely creeping on hard substances ; when disturbed they fall or 

 sink, and remain a long time immoveable before they reappear at the surface. 



(4) This animal, when it swims or creeps, covers its shell with the two dentated 

 lobes of its mantle. 



