THE 



QUARTERLY JOURNAL 



OF 



THE GEOLOGICAL SOCIETY OF LONDON. 

 Vol. LXVIII. 



1. The Evolution op Inoceramus in the Ceetaceotjs Period. 

 By Henry Woods, M.A., F.G.S., University Lecturer in 

 Paleeozoology, Cambridge. (Read November 22nd, 1911.) 



Intkoductor? Remarks. 



Although the genus Inoceramus is found in deposits as early as 

 the Lias, yet it is represented by comparatively few species until the 

 close of the Lower Cretaceous Period, after which it underwent 

 rapid evolution so that many species and varieties were developed ; 

 but, so far as we know, none of these survived the Cretaceous Period 

 or left descendants. From the evidence which has been furnished 

 by a study of the variation of the species, their zonal distribu- 

 tion, morphological resemblances and development, and from the 

 discovery of connecting links, it now seems possible to recognize 

 the main lines of evolution in the Inocerami of the Cretaceous 

 Period. 



The species of Inoceramus found in the Gault, the Upper 

 Greensand, and the Chalk appear to have originated from two 

 stocks which occur in the Lower Greensand (Aptian), one being 

 J. salomoni d'Orh., the other belonging to the type of /. neocomiensis 

 d'Orb. and I. ewaldi Schliit. 



Q. J. G. S. No. 269. b 



