GASTEROPODA. 



251 



witluli the influence of fresh water, and frequently become dis- 

 torted ; similar monstrosities are found in the Norwich crag. 



Fig. 104. Littorina littorea. (Warington.) 



The common species (Z. littorea) is oviparous ; it inhabits the 

 lowest zones of sea-weed between tide-marks. An allied species 



r, rostrum or muzzle. 

 k, buccal mass. 

 g, nervous ganglia 



(reproductive orifice, on 



the right side). 

 s, salivarj' gland, 

 ee, oesophagus, 

 I, lingual coil. 

 m, slieU-niuscle. 

 6, branchia or gill. 



c, heart, 

 n, aorta. 



e, stomach. 

 /, liver. 



h, biliary canal, 



f, intestine, 

 a, anus. 



0, ovary. 



d, oviduct, 

 w, uterus. 



0', ovarian orifice. 

 X, renal organ. 

 y, mucus gland. 



Fig. 105. Littorina litter alls P: (after Souleyet). Animal removed from its shell; 

 branchial cavity and back laid open. 



(i, rudis) frequents a higher region, where it is scarcely reached 

 by the tide ; it is viviparous, and the young have a hard shell 



