FRESH-WATER AND MARINE FORMATIONS. 
55 
Fig. 24. 
Planorhis euomphalus, Sow.; 
fossil. Isle of Wight. 
Fig. 25. 
Limncea longiscala^ 
BroDg.; fossil. Isle 
of Wight. 
Fig. 26. 
Paludina lenta, Brand.; 
fossil. Isle of Wight. 
The univalve shells most characteristic of fresh-water de¬ 
posits Planorhis^ Limncea^ Paludina, (See figures.) 
Fig. 2T. Fig. 28. 
Fig. 29. Fig. 30. 
Succinea amphibia, Ancylus velletia {A. 
Drap. (S. pntris, L.); elcgam), Sow.; fossil, 
fossil. Loess, Rhine. Isle of Wight. 
Valvata piscina- Physa liypno- 
Us, Mull.; fos- rum, Linne ; 
sil. Grays, Es- recent. Isle 
sex. of Wight. 
But to these are occasionally added Physa^ Succinea^ Ancy- 
lus^ Valvata^ Melanopsis^ Melania,^ Potainides^ and Neritina 
(see figures), the four last being usually found in estuaries. 
Fig. 31, 
Fig. 33. 
Fig. 34. 
Auricula; recent. 
Ava. 
Melania inquinata, 
Def. Paris basin. 
Physa columnaris, 
Desh. Paris basin. 
Melanopsis buccinoidea, 
Ferr.; recent. Asia. 
Fig. 35. 
Fig. 36. 
Some naturalists include Neritina (Fig. 35) and the ma¬ 
rine (Fig. 36) in the same genus, it being scarcely 
possible to dis¬ 
tinguish the two 
by good generic 
characters. But, 
as a general rule, 
the fluviatile spe- 
Neritirm globulus, De£ 
Paris basin. 
Nerita granulosa, Desh. 
Paris basin. 
