363 



PULMONIFERA ; SNAILS. 



The ONCIDIID.E are nearly allied to the slugs. They are com- 

 pletely covered with a coriaceous mantle, which is broader than 



FIG. 660 TESTACET.I.A 



ap p 



the foot, but contains no shell. Their usual residence is on 

 aquatic plants, in the marsty districts of warm climates ; but 

 several species are found on the sea-shores, where they dwell 

 within reach of the waves. 



982. The Snails, and their allies, constituting the family 

 HELICID^E, are closely allied to the Slugs in organisation ; differ- 

 ing in but little else than the possession of a shell, into which the 

 body may be withdrawn. The Common Garden-Snail of this 

 country, and the Helix pomatia^ or Edible Snail of France and 



Italy, are well- 

 known examples 

 cv of this family. 

 More striking ones 

 are to be found, 

 however, in tro- 

 pical climates. 

 Among the mem- 

 bers of this group, 

 we may especially 

 notice the genus 

 Anastoma, which 



FIG. 661. ANATOMY OF SNAIL; /, foot; f, tentacula half IS distinguished by 

 contracted; d, a sort of diaphragm, separating the respira- .1 -v^.,1;.,,. fnrm 

 tory cavity from the other viscera ; s, portion of the sto- l 



mach ; I, liver; o, ovary ; i, intestine; r, rectum, or last and position of the 

 part of the intestine; a, nus ; ft, heart; ap, pulmonary . _ , , .. 



artery, distributed over the walls of the pulmonary cavity, mouth Ot the Shell 



p ; ar, aorta; v, secreting gland for the mucus which in the adult 

 covers the body ; cv, its excretory duct, opening near the 



anus. ing its early life, 



ita mouth is in the same position as that of other snails ; 



