UNIO VALDENSIS. 30.3 



rivers of North America, present a striking con- 

 trast with the few and homely British species. In 

 a fossil state Uniones are rare ; a few occur 

 in the carboniferous strata, and these with eight 

 or nine small species from the Wealden, figured by 

 Dr. Fitton and myself, comprise all that are known 

 in our secondary strata. 



Many of the slabs of limestone procured from 

 Sandown Bay, and used in the pavements at 

 Brading, Ryde, &c. display sections of a species 

 of Unio, which is common in some of the Pet- 

 worth and Purbeck beds. On a visit to Brook 

 Point in 1843, I discovered a remarkably fine and 

 large species of Unio in the cliff above the petri- 

 fied trees, and have since collected many specimens 

 of this interesting fossil, which I have proposed to 

 distinguish by the name of Unio Valdensis, or 

 Wealden river-mussel. A small and young example 

 is figured in PL VI. fig. 1 ; the hinge, and the an- 

 terior muscular imprints, are shown in the upper 

 figure. The specimens obtained from the cliffs 

 are in an excellent state of preservation ; the sur- 

 face of the shell, which is but little worn, is of a 

 tawny-red colour, like some of the recent Ohio 

 species. Even the horny ligament with its trans- 

 verse rugae remains ; and in some instances the 

 shell is occupied by the body of the animal in the 



