Vol. 52.] A DELIMITATION OF THE CENOMANIAN. 129 



) Feet. Jns. 



Bubbly broken cbalk and soil 6-7 



Smooth glauconitic cbalk in two massive bed3, weathering 



with a peculiar mealy touch when handled 5 



Eough, lumpy, grey, glauconitic chalk, hardly nodular, but 

 lumpy, the lumps being hard, with soft mealy chalk 

 between, very fossiliferous 6 6 



At or near Orbec are several large pits at this horizon showing 

 the lowest part of the Cenomanian, but without exposing the actual 

 base. The most important is a quarry close to the railway, halfway 

 between the stations of Orbiquet and St. Martin de Bienfaite. 

 Nearly 40 feet of chalk is here exposed and its general character 

 may be understood by the following section. Descending order : — 



Feet. Ins. 



Smooth, yellowish -grey, mealy chalk, rather glauconitic ... 2 6 



Rough chalk, lumpy, the lumps being in a mealy matrix . 2 



Soft, yellowish-grey, mealy chalk with grey cherts 7 



Bough, glauconitic, yellowish-grey chalk with hard lumps 



in a softer mealy matrix 5 



Firm, glauconitic, yellowish-grey chalk 2 



Firm, glauconitic, yellowish-grey chalk, with hard silicifled 



masses — not chert 3 



Softer glauconitic chalk, weathering in platy pieces 2 6 



Bed of large separated cherts 6 



Firm, yellowish-grey, glauconitic chalk, smooth, without 



lumps 9 



A course of hard, lumpy, glauconitic chalk 3 



Smooth, whitish-grey, glauconitic chalk 1 6 



Although the general character of the chalk seen in this quarry 

 agrees with that at the same horizon in this and other localities, we 

 are unable to correlate the various beds, and it would appear that 

 minor peculiarities do not persist in the way that frequently happens 

 in the English Chalk. The rock at this horizon is usually yellowish, 

 or ochreous white, or grey in colour, slightly but irregularly glauco- 

 nitic, some beds containing more glauconite than others, the grains 

 being small. It weathers down and gives off a dust which has a 

 somewhat gritty, mealy texture, and is not the impalpable powder 

 which results from the handling of English chalk. 



It contains many concretions of a siliceous nature, sometimes 

 merely silicified chalk; but often there is a nucleus of clear black or 

 grey silica, which merges through the silicified chalk into the calca- 

 reous matrix which surrounds it, there being no rind. Well-defined 

 chert-nodules are, of course, also common. 



2. Northern Orne. 



Continuing the exploration of the Touques Valley, evidence of the 

 outcrop of the Green sand was met with in several localities, but no 

 section was seen until Fauvaque was reached. Here a small quarry 

 showed Greensand still underlain by a thin bed of clay, which in 

 its turn rested directly on the Corallian — the Carstone-like bed being 

 absent. 



