214 



ZOOLOGT 



shown by the enormous variabihty of individual species. 

 Thus in our own country a species, Helix nemoralis, introduced 

 from Europe, has produced at Lexington, Virginia, 385 varieties 

 in an area not over one-half mile in extent. These variations 

 consist of different combinations of ground 

 color and of stripes on the shell. But the 

 wTm animal itself is eciuallj^ variable, for any 



W|F species of Helix, collected in large numbers, 



I will show individuals having abnormalities 



Fig. 201. — Meiam- both in regard to the number of tentacles 

 pus, the salt-marsh ^t^^ gf py^g ypon each tentacle. Besides 



.snail. Nat. size. 



Piioto. by W. H. Helix, a very abundant cosmopolitan land 

 pulmonate is Pupa.' The shell is many 

 times whorled, and has a blunt apex. Being of small size, it 

 is, however, less commonly known. It is found in woods 

 under leaves or in old stumps and decajdng logs, where it 

 feeds. It is a lover of darkness, moisture, and contact. 



Intermediate between the terrestrial and aquatic pulmonates 

 is the family Auriculidae, the members of which live on the 

 seashore, in salt marshes (Fig. 

 200), or on rocks where they may 

 even he immersed in brackish 

 water at high tides. One of the 

 commonest forms is Melampus 

 (Fig. 201), found among the roots 

 of marsh-grass. 



Of the aquatic pulmonates three 

 genera are common and easily 

 chstinguLshable. Limnaea,^ the 

 " pond snail," is common in 



Fig. 202. — Left Physa, hetero- 

 s(rop}ia, the left-handed pond 

 snail. Right, Limna!a, the right- 

 handed pond snail, with the 

 apex eroded off as is usually the 

 case in adult shells. Nat. size. 

 Photo, by W. H. C. P. 



A little girl or doll. 



2 From limne, a marsh. 



