GASTEROPODA. 251 
within the influence of fresh water, and frequently become dig- 
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 
° 
7, rostrum or muzzle. : 
k, buccal mass. \ / 
g, hervous ganglia ; 
(reproductive orifice, on 
the right side), 
S, Salivary gland. 
@, cesophacus, 
2, lingual coil. 
m, shell-muscle, 
6, branchia or gill, 
c, heart. 
n, aorta. 
e, stomach, 
J; liver. 
h, biliary canal, 
i, intestine, 
a,anus, 
0, ovary. 
d, oviduct. 
u, uterus. 
o', ovarian orifice, 
z, renal organ. 
y, Mucus gland, 
Fig. 105. Littorina littorahs P: (after Souleyet). Animal removed from its shell , 
branchial cavity and back laid open. 
(Z. rudis) frequents a higher region, where it is scarcely reached 
by the tide; itis viviparous, and the young haye a hard shell 
ane. 
