42 
NERITIDJE. 
phrodite^ self-impregnating (?). Shell spiral, or 
conical, symmetrical. 
With the single exception of Neritina and Proser^ 
pina^ all the animals of the sub-order are marine. 
Fam. 1. NEEITli)^; 
Muzzle very short, annulated, provided with a hood ; 
jaws two, one above and the other below, both 
toothed on the edge. Tentacle contractile, subu- 
late, pointed. Eyes on short pedicles at the base 
Fig, 11. 
a, foot below ; 6, head above ; c, operculum inside. 
of the tentacles (fig. 11. A.). Tongue membrane 
broad, with very numerous series of transparent 
glass-like teeth; the central teeth (fig. 12.) very 
Fig. 12. 
unequal; the second and fifth on each side 
large, broad, dark-coloured; the lateral teeth 
