GASTEROPODA. 107 



to the axis of the shell ; having the margins disunited by 

 the projection of the last volution. The Helices, or Snails, 

 which are very numerous, and present considerable differ- 

 ences in the form of the shell, have by several more recent 

 authors been arranged into various subgenera. 



Helix arhustorum The Grove Helix. Plat* XIII. 



fig. 27. Subglobular, subumbilicated, finely striated longi- 

 tudinally ; greenish-yellow or reddish, beautifully mottled, 

 and streaked with reddish-brown, and a broad brown band 

 running throughout the middle of the volutions. One inch 

 in diameter. Inhabits the thickets and woods of Europe. 



ORDEE n.-GASTEROPODA. 



Animals with straight bodies, and never spiral, nor en- 

 veloped entirely in a shell, having a foot or muscular disk 

 under the abdomen, attached to the body nearly its whole 

 length, and serving for progressive motion. 



Section I — Pneumobranchi^. 



Branchiae constructed like a vascular net, on the wall 

 of a particular cavity, opening by a perforation which the 

 animal has the power of contracting and dilating at pleasure. 

 They respire air. 



TRIBE I. LIMACINEA. 



The animals almost wholly naked, with elongated bodies ; 

 and creeping by means of a ventral disk ; branchiae in the 

 form of a vascular network, lining a cavity, of which the 

 aperture is a hole capable of being contracted or dilated at 

 will. 



Genus 1.— VITRINA— Za/narcA. 



Generic Character, — Body creeping, elongated, snail- 

 shaped, nearly straight ; posteriorly separated from the foot. 



