428 TEXT-BOOK OF ZOOLOGY 



This fold, which partially or wholly envelops the body, is known as the 

 mantle, or pallium, and the cavity as the mantle cavity, or pallial chamber. 

 The latter is also known as the " branchial (or pulmonary) chamber," 

 since it encloses the branchiae, or functions as a lung. On its external 

 surface the mantle secretes a shell, which protects the soft body of the 

 animal. In regard to other forms of mollusc, see the respective illustra- 

 tions. Most of the Mollusca propagate themselves by eggs. 



Sch. 



Structure of Roman or Vineyard Snail (Diagrammatic). 



F., Foot; R., body; Ko., head; Fii., feelers; Mt., mantle; R.Mt., free edge of mantle; 

 Mh. , mantle cavity ; At. , respiratory aperture (the entrance to the mantle cavity is 

 indicated hy an arrow) ; Sch., shell ; M., mouth ; D., intestine ; A., anus. 



CLASS I. : SNAILS, SLUGS (GASTROPODA). 



Mollusca with an asymmetrical coiled visceral sac, well-developed head, 

 and sole-shaped foot occupying the central portion of the ventral surface ; 

 mostly with a spirally-coiled shell, more rarely naked. 



ORDER I. : AIR-BREATHING GASTROPODS 

 (PULMONATA). 



The Roman or Vineyard Snail (Helix pomatia) .* 

 (Length of extended foot up to 3£ inches.) 



A. Topography of Structure. 



In considering the structure of this animal, we must append the following 

 additional remarks : The anterior termination of the grayish- white body 



* This species is much larger than our common snails, and, although common in Germany, 

 is only found is certain localities in England, e.g., near Oxford. The structure of a common 

 garden snail (Helix hortensis) is quite similar. 



