

404 THE WONDERS OF GEOLOGY. Lect. IV. 



The fresh-water mussels called Uniones, from their solid 

 pearly shells, occur in considerable abundance in some of 



Lign. 97. — Wealden shells, from Pounceford, Sussex. 

 a, Melanopsis tricarinata;* b, Cyclas media; c, Cyclas membranacea. 



the Wealden strata, but the species are, for the most part, 

 of small size. But I discovered, not long since, a remark- 

 ably fine and large Unio, in the cliff at Brook Point, im- 

 bedded with the fossil trees (ante, p. 379). I have named 

 it Unio Valdensis, or Wealden mussel. These shells are 

 from four to six inches long, and well preserved ; the surface 

 is of a tawny red colour, the horny ligament, with its 

 transverse rugae remains, and in some examples the shells 

 are occupied by the body of the animal in the state of mol- 

 luskite.f The collocation of these large mussels with the 

 drifted trees and bones of terrestrial reptiles, in strata 

 so manifestly of fluviatile origin, completes the analogy 

 between the rafts imbedded in the delta of the wealden, 



* This shell is the Potamides carbonarius of Homer, and is abun- 

 dant in weald clay at Neurladt, in Hanover. 



+ See Geology of the Isle of Wight, p. 303, for the description, and 

 PL VI. Jig. 1, for a figure of this fine fossil shell, which resembles 

 some of the Uniones of the American rivers. Also the London 

 Journal of Geology; Plate XIV. 



