MIDDLE CHALK—NORTH OF FRANCE. 
497 
is quarried for the manufacture of cement. M. Bizet describes 
the succession as follows ;—* 
1. Chalk with Terebratella Bourgeoisi (seen near Nogent le Rotrou). 
2. Marly chalk with Rhynchonella Cuvieri and Inoceramus labiatus. 
3. Glauconitic chalk, with Terebratella carantonensis and Ditrupa deformis. 
The lowest bed may possibly represent the zone of Actinocamax 
plenus, and it certainly recalls the sandy glauconitic chalk which 
contains that fossil and occupies a similar position on the coast 
of Devon ; its thickness is only a metre (about 3 feet). 
The zone of Inoceramus labiatus is described as a white marly 
chalk, more or less compact, with some layers of black flints, but 
containing very few fossils except the two above mentioned and 
Ostrea columba ; its entire thickness may be about 30 feet. This 
marl makes good cement, and M. Bizet gives 
samples from different places, as below : — 
Analyses of “ Craie marneuse." 
analyses of three 
L’Aigle. 
Irai. 
Senouche. 
Residue insoluble in acids 
- 14*70 
14*90 
16*35 
Alumina and peroxide of iron - 
*80 
•85 
•80 
Lime. 
- 43*50 
36-65 
43-25 
Magnesia. 
*50 
. -45 
•25 
Loss [carbonic acid], etc. 
* 40*50 
47*15 
39*35 
100-00 
100-00 
100-00 
Another sample from Remalard, east of Belleme, was still more 
argillaceous, yielding 26'25 per cent, of insoluble residue, with 
G' 30 of alumina and oxide of iron, and with only 32'45 of lime. 
This sample cannot therefore have more than 57 per cent, of 
calcium carbonate, while the others have probably from 65 to 
70 per cent. This change from the calcareous facies of Rouen and 
Fecamp to a deposit resembling our chalk marl is very noteworthy. 
One of the most westerly exposures of this marl is on the road 
from Verneuil to Alencon, showing : — 
feet 
Marly chalk, with Inoceramus labiatus - - - 16 
Yellowish marly chalk - y - - - 1 
Glauconitic marl, with Ditrupa deformis 3 
Sands of the" Upper Cenomanian - seen for 16 
In the Sarthe, according to Guillier,! the basement bed of the 
Turonian is a quartz-sand, more or less coarse, sometimes compacted 
into sandstone by a calcareous cement. This sand varies in thick¬ 
ness from 3 to 30 feet, and is characterised by Ostrea columba, 
Catopygus obtusus, Nucleolites parallelus, and Rhynchonella Cuvieri. 
This is succeeded by a glauconitic chalk about 6 feet thick, contain¬ 
ing Terebratella carantonensis, Terebratula phaseolina, and small 
* Bull. Soc. Geol. Norm., Yol. ii. p. 74. 
t Geologie du department de 1a. Sarthe, 1886, p. 266. 
