28 VIVIPAEID^. 



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 Ilydrohia 

 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. VIVIPARIDiE. 



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. 



