LOWER CHALK—NORTH-EAST OF FRANCE. 
230 
The Wissant type of Cenomanian can be followed all round the 
Boulonnais, but the total thickness probably diminishes somewhat 
to the southward. 
Country of the Tourtias— Pernes, Mens, and Tournay. — Passing 
over the Chalk country south-east of the Boulonnais we find the 
Cenomanian cropping out again in the country to the south-west 
and south of Bethune. This region has been described by Mons. H. 
Parent.* His identification of a zone of Pecten asper overlain by 
a zone of Ammonites laticlavius has been mentioned in the first 
volume of this Memoir, and whether the latter or the former is 
regarded as the basement bed, it would seem that there is near 
Bernes and Matringhem a Lower Chalk similar to that of Folke¬ 
stone and Wissant, but much diminished in thickness. The section 
at Pernes is as follows :— 
M 
ft. in. 
6. Compact marly chalk - - - - - - - 4 0 
5. Marly chalk, slightly shaly and glauconitic - - - 2 6 
4. Marly glauconitic sand - - - - - - - 26 
3. Sand with more glauconite - - - - - - 34 
2 . Greensand with many phosphatic nodules - - - 2 0 
1. Brownish clay, slightly glauconitic, resting on the up¬ 
turned Devonian - - - - - - - - 26 
16 10 
Of these beds M. Parent refers 5 and 6 to the zone of Holaster 
subglobosus, 3 and 4 to that of Ammonites laticlavius ; No. 2 is his 
zone of Pecten asper , which we have already accepted as such; 
the fauna of No. 3 is certainly that of the Chloritic Marl of 
the Isle of Wight, for in it occur Ammonites varians, A. Coupei, 
A. Mantelli, Turrilites Morrisi, T . tuberculatus, T. costatus, Bacu- 
lites baculoides, Nautilus deslongchampsianus, N. Icevigatus, and 
N. largilliertianus, with many other fossils. 
As regards the higher part of the stage M. Parent says : “ I have 
only observed the upper part of the zone of Hoi. subglobosus at 
a few spots ; to the north of Houdain it occurs as a chalky marl 
with Rhynchonella mantelliana, Rh. grasiana, Kingena lima, 
Plocoscyphia mceandrina. At Pernes, on the road from Bailleul- 
les-Pernes there is a marly chalk containing Holaster trecensis, 
lnoceramus virgatus ( striatus, Sow.,) and In. orbicularis ( latus, 
d'Orb), which I refer to this zone.” 
Of the zone of Belemnitella plena he says : “ The only place where 
I have seen the marl with Belemnites plenus characteristically 
developed is near Fauquembergne; it forms part of the hill which 
rises to the east of the village, and contains B. plenus at the base. 
It occurs again in a gully to the left of the road from Fruges, and 
at ‘ Bout de la Ville ’ in a quarry.” 
The most easterly quarry described by M. Parent at Aix-en-Gohelle 
shows a curious and significant section, as follows : — 
* 
Ann. Soc. Geol. du Nord, Tom. xxi. p. 205 (1893). 
