Dr. FiTTON on the Strata below the Chalk. 327 



within which a very sh'ght elevation of the central tract has brought into view the subjacent 

 strata, as far down as those which immediately precede the representative of our Oxford oolite, 

 with perhaps the mountain limestone beneath. I have not myself examined this interesting district ; 

 and the only publications relating to it that I have seen, are the report of the proceedings of the 

 Geological Society of Paris during their excuision to Beauvais in 1831 *, and the splendid work 

 of M. Passy on the Geology of the Department of the Lower Seine-j- : — but from the notes and 

 sectional sketch of M. Cordier in the former of these works, and the full descriptions of M. Passy, 

 there can be no doubt that the strata in the Pays de Bray are the same with the upper part of the 

 series in the Lower Boulonnois. 



The following is the order of the strata in the Pays de Bray, with what appear to me to be 

 their equivalents in England ; my list of equivalents, I am glad to find, coinciding very nearly 

 with that of M. Passy himself t. 



1. La Craie. — (Chalk). 



2. Glauconie sableuse de la craie. — (Upper Green-sand). 

 Fossils said to be the same as of the Lower Chalk. 



3. Marne micacee et Marne bleue. — (Gault). 



Divisible, (at Ferte en Bray) into two portions : — 1. Brown and micaceous. 2. Blue. At Meulin 

 the blue marl is about 50 feet thick ; it abounds in iridescent fossils, among which are, Ammonites 

 splendens; Hamites intermedius ; Inoceramus sulcatus; Nucula pectinata. 



4. Gres, et sable, Glauco-ferrugineux. — (Lower Green-sand). 



At Cap la Heve are two beds of sand and ferruginous conglomerate, separated by a micaceous 

 and glauconious marl. Quce. the three subdivisions of Folkstone ? ?. At Forges and Neufchatel 

 the ferruginous sand is 70 feet thick : it occurs above the Argile bigaree, mentioned hereafter, 

 and contains, among other fossils, Gryphcea sinuata. At Les Friches de St. Germain is iron ore 

 in grains, including small portions of ochreous hydrate of iron, with marine shells. 



5. Argile bigaree (Glaise Marbre.) — Variegated marl clay, and, sand, — (of the Wealdenj 



— or Beds subordinate to the Lower Green-sand.) 

 This deposit, which, according to M. Passy, is found everywhere in the Valley of the Pays de 

 Bray, seems from the description to be very like the variegated sandy clay of the Wealden ; but 

 at St. Paul, near Beauvais, it is said to contain marine shells, the species of which, however, are 

 not mentioned. Its place is commonly below the first stage of ferruginous sand and grit, and above 

 the Argile a fougeres ; a situation corresponding to the place of some of the Wealden marls. 



6. Argile a creusets ; Argile de Forges ; Argile a fougeres. — (Weald-clay). 



This clay in one place, at Neufchatel, is extracted by means of a shaft 70 French feet in depth, 

 and occurs beneath sand of diflPerent shades, belonging to the Glauco-ferruginous beds, No. 4. above. 



At St. Germaine la Poterie, a bed of slaty clay (lignite) is found, containing impressions of 

 Lonchopteris Mantellii, and from one to two metres thick §: and among the beds found by M. 

 Graves near Songeons, is one, described as " Marbre d'eau douce a Paludines," and referred by him 

 to the Purbeck strata ||. 



There can be little doubt, therefore, that some equivalent of the Wealden beds exists in this 

 tract ; but M. Passy appears to me to be in error when he is led, (no doubt by the indistinctness 

 with which the strata are developed and exposed in the Pays de Bray), to regard the Wealden 



* Bulletin de la Societe Geologique de France, 1831, p. 1. to 23. 



t Description Geologique du Departement de la Seine Inferieure, 4to, Rouen, 1832. 



X Passy, p. 237 to 272 ;— and Plates L IL IIL IX. and XVII. fig. 1. 



§ Passy, p. 255. 1| Ibid., p. 257. 



YOL. IV. SECOND SERIES. 2 U 



