A MONOGRAPH 



OF 



THE CRAG MOLLUSCA 



OR, 



DESCRIPTIONS OF SHELLS 



FROM THE 



MIDDLE AND UPPER TERTIARIES OF THE EAST OF ENGLAND. 



BT 



SEARLES Y. WOOD, F.G.S. 



PART II. 



BIVALYES. 



LONDON: 



PRINTED FOR THE PAL^ONTOGRAPHICAL SOCIETY. 

 1850. 



