28 
VIVIPARID^. 
135^ f. 122.) I take to be the young of P. similis 
{Bithinia ventricosa)^ judging from specimens in Mr. 
Clark’s cabinet.” Most probably this idea is correct^ 
as I have not been able to find any authority 
for Draparnaud’s species being found in this coun- 
try ; and it is to be remarked that Turton’s account 
is taken from Draparnaud^ and Dr. Turton does not 
give any habitat for the species. M. N. Boubee’s 
specimen of Pal. viridis proves it to be a Hydrohia 
or minute Littorina : it has a horny subspiral oper- 
culum. 
Mr. Alder also thinks that the Paludina stagno- 
rum Turton^ Man. (ed. 1. 136. f. 123.) may probably 
be a mere slender variety of this species. {Mag. 
Zool. and Bot. ii. 116.) I think it is much more 
probably a Littorina^, as he considers it the same as 
Paludina acuta of Drap. In the absence of speci- 
mens, it is impossible to decide ; and, as Dr. Turton 
does not give any locality, it is even doubtful if the 
whole account of the species and figures were not 
derived from Draparnaud’s work. If intended for 
any British species, it must be Littorina ventricosa^ 
which is common in the ditches with Cardium edule^ 
&c. near Tilbury Fort. 
Fam. 4. VIVIPAEID^. 
Head annulated, contractile, broad, extended to the 
plane of the foot. Teeth in 7 longitudinal 
series; the lateral broad, ovate, converging. 
Jaws 2, lateral, horny, narrow, sharp-edged. 
