GASTEEOPOLA. 



251 



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

 torted ; similar monstrosities are found in the Norwich crag. 



Fig. 104. Littonna littorea. (Warington.) 



The common species {L. littorea) is oviparous ; it inhabits the 

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



r, rostrum or muzzle. 

 A", buccal mass. 

 g, nervous ganglia 



(reproductive orifice, oa 



the right side). 

 e<f, salivarj' gland. 

 oe, oesophagus, 

 /, lingual coil. 

 m, shell-muscle. 



b, branchia or gill. 



c, heart. 

 n, aorta. 



e, stomach, 



/, liver. 



h, biliaiy canal. 



t", intestine. 



rt,anu8. 



0, ovary. 



d, oviduct. 

 u, uterus. 



o', ovarian orifice. 

 X, renal organ. 

 y, mucus gland. 



Fig. 105. Littorina Uttoralis P : (after Soulcyet). Animal removed from its shell , 

 branchial cavity and back laid open. 



[L. rudis) frequents a higher region, where it is scarcely reached 

 by the tide ; it is yiyiparous, and the young hayc a hard shell 



