Silurian and Devonian Systems. 165 



light on the English succession, and it seems desirable to give here 

 a resume of the conclusions reached. 



I. NOTES ON THE SUCCESSION IN BELGIUM, NORTH 

 FRANCE, AND ENGLAND. 



A. The Ardennes. 

 The generalized section of the base of the Devonian in the 

 Ardennes is as follows : — 



„ .. . , . rSchistes de Saint-Hubert. 



Gedinmen superieur . . (schistes d'Oignies. 



C Schistes de Mondrepuits. 

 ^ T . . ,, . Arkose de Haybes and 



Gedmnien inferieur . . ^ Arkose de Weismes. 



V Poudingue de Fepin. 

 Well-marked unconformity. 



Cambro-Silurian rocks, of which the most recent are of Wenlock and 

 Lower Ludlow age. 



The fauna of the Lower Gedinnian is not a large one, and has 

 fortunately been reviewed in recent years by Professor Leriche 

 in "La faune du Gedinnien inferieur de I'Ardenne " } The fauna 

 there described comprises thirty-three species, excluding the 

 Ostracoderms, described elsewhere by the same author.^ 



(a) Gedoumont, near Malmedy, Belgian Prussia. 

 Here the Lower Gedinnian, resting on Cambrian, is represented 

 by a white sandstone (Gres de Gedoumont), which is perhaps the 

 equivalent of part of the Schistes de Mondrepuits as well as the 

 Arkose de Haybes. By far the most abundant fossils are Chonetes 

 striatella, and a Rhynchonellid, identified by Leriche as Rh. nucula. 

 It is a small form, apparently identical with the small form I have 

 called Rh. nucula var., and noted as characteristic of the Upper 

 Chonetes Flags in Shropshire.^ It occurs also in the Platyschisma 

 shales. The association of these two fossils is at once striking and 

 suggestive to one who has studied the Upper Chonetes Flags of 

 Shropshire. Occurring commonly also in the Gres de Gedoumont 

 are Orthis cf. lunata, Pterincea retrojlexa, and corals {Petraia hina 

 and Cysti'phyllum profundum). The Devonian affinities of the fauna 

 are seen especially in the occurrence of Cryphceus and numerous 

 examples of Spirifer Dumonti (de Koninck). The latter may prove 

 to be a derivative of Sv- elevatus. 



(b) Gilejjpe, near Verviers. 

 Here the Gedinnian rests on Salmian rocks with Dictyonema 

 sociale. The locality is to the north of the last (north of the 

 " massif " of Stavelot), and the deposits are of the type generally 

 referred to as Old Red Sandstone. They consist of rubbly green or 

 red shales, with abundant cornstones, very closely resembling some 



1 Mem. Musee royal d'Hist. nat. de Belgique, vol. vi, 1912. 



2 Mem. Soc. geol. du Nord, vol. v, 1906, pp. 26-39. 



3 Loc. cit., p. 231. 



