FOSSIL FRESH-WATER BIVALVES. 415 
Tilg. For. p. 57), and subsequently found in numergus 
localities of the Wealden.” ® 
In 1844 I discovered a large species in the Wealden at 
Brook Point. I have named it Unio Valdensis.t 1 have 
collected and obtained nearly fifty specimens; they present 
two varieties, the one 
contracted and narrow, 
the other broader and 
deeper; this difference 
is probably sexual; the 
wide and deep shells 
may be the females; for 
in the living American 
Uniones the same cha- 
racters are observed. 
Some examples are re- 
markably well  pre- 
served; the ligament 
remaining in a carbon- 
ized state, and the body 
of the mollusk in the 
condition of molluskite; 
even a tint of the origi- 
naltawny reddish colour 
of the shell is present. 
The same species has been found in the Wealden strata, 
near Tunbridge Wells, by Mr. Barlow, C. E. 
I shall reserve my remarks upon the important aid these 
Lien. 131. Unio VALpENSIs. (3 nat.) 
Wealden ; Isle of Wight. 
* They are figured in Geol. S.E. p. 250; and in Dr. Fitton’s 
Memoir, Geol. Trans. vol. iv. pl. 21. 
+ Unio Valdensis resembles in form the Mexican species, U. Pana- 
coensis (River Panaco), but is probably more nearly allied to an un- 
named Australian species of which Mr. G. Sowerby has numerous 
examples. P 
