A MONOGRAPH 



OF 



THE CRAG MOLLUSCA, 



WITH 



DESCRIPTIONS OF SHELLS 



PROM THE 



UPPER TERTIARIES OF THE BRITISH ISLES. 



BY 



SEARLES Y. WOOD, F.G.S. 



VOL. I. 



UNIVALVES. 



LONDON: 



PRINTED FOR THE PALiEONTOGRAPHICAL SOCIETY. 



1848. 



