Meports and Proceedings — Geological Society of London. 283 



divisions. The entire Flora and Fanna of the Wealden formation 

 has a Jurassic character, and the relations of the Lymneen and 

 Brackish-water deposits of the Wealden with the Marine beds of the 

 Portland, aiford evidence of the alternation of conditions which 

 prevailed during the close of the Jurassic epoch. 



The plates which illustrate the Monograph are beautifully executed. 



The number of species amounts to 146, of which there are — 



Plants 33 species belonging to 24 genera. 



> )» ^ 



,. 6 



Conctiifera 



62 



Gasteropoda 



21 



Annulata 



1 



Insecta 



1 



Crustacea 



8 



Fish 



18 



Eeptiles 



2 



146 51 



The construction of the Paljeontological table and catalogue of 

 species is to be highly commended, seeing that it brings before the 

 eye at a glance the most important points connected with the history 

 of the Fauna and Flora of the Wealden and associated formations. 

 One column contains the name and synonym of each species, another 

 the literature of the same, a third their distribution in the Kim- 

 meridge and Portlandian, a fourth in the Purbeck and Wealden, and 

 a fifth contains localities and general remarks thereon. All students 

 who aim at precise and concise methods in order to represent the 

 ancient life history of any formation may well take a lesson from 

 these tables. This work will be welcomed by all geologists who 

 take an interest in the marvellous chapter of the Earth's history to 

 which it relates, and especially so to English naturalists acquainted 

 with the correlated beds of the Wealden in our Southern Coast 

 sections, which they can now compare with those in the neighbour- 

 hood of Hanover. J. W. 



GrEOLOGICAL SOOIETT OF LoNDON. 



April 27, 1881.— Eobert Etheridge, Esq., F.R.S., President, in 

 the Chair. — The following communications were read : — 



1. "On the Precise Mode of Accumulation and Derivation of the 

 Moel Tryfan Shelly Deposits ; on the Discovery of similar High- 

 Level Deposits along the Eastern Slopes of the Welsh Mountains ; 

 and on the Existence of Drift-zones showing probable Variations in 

 the Eate of Submergence." By D, Mackintosh, Esq., F.G.S. 



The author commenced by giving a sketch of the progress of dis- 

 covery connected with the Moel Tryfan deposits. He then described 

 certain phenomena connected with these deposits, to which little or 

 no attention has been devoted by other observers. After identifying 

 the local stones, and indirectly local erratics, he traced the derivation 

 of the far-travelled erratics which came from the N. and N.W. He 

 drew particular attention to an extensive exposure of slaty laminae, 



