Mr. Weavei' on the Structure of the South of Ireland, 389 



In the Ardennes, the clayslate tract {terrain ardoisier), re- 

 ferred to the Cambrian system, is divided into three stages: 

 the lower destitute of fossils; the medial, in which roofing 

 slate abounds, but in which few fossils have hitherto been 

 found; and the upper, more quartzose than slaty, in which 

 the vestiges of life begin to acquire greater extension, and in 

 which the first indications of limestone appear, the latter 

 being generally slaty, containing numerous crinoidal remains, 

 and forming beds about a yard in thickness, but never occur- 

 ring: ill mass like the limestone of the anthraciferous tract. 

 In this upper stage M. Dumont notices Orthoceratites, Cri- 

 noidea, Polyparia, Trilohites^ Strophomena, &c.; but accord- 

 ing to M. d' Omalius d' Halloy, the most common fossils which 

 it displays are Spiriferce greatly expanded in the direction of 

 their breadth, besides species referable to the genera Caly- 

 mene, Asaphus, Orthuceras, Hamites, Leptcena, Strophomena, 

 and remains of Crinoidea and Polyparia''^. M. d' Halloy 

 admits that the fossils of this clayslate tract have not been 

 determined with sufficient exactness. Yet as far as developed 

 by himself and M. Dumont, can it be safely maintained that 

 a precise analogy has been established between them and 

 those found in the Cambrian system ? 



The clayslate tract, thus referred to the Cambrian system, 

 passes in its upper stage by insensible gradations into the 

 anthraciferous tract f? both on the north-western and south- 

 eastern sides of the Ardennes; in the former direction in Bel- 

 gium, and in the latter in the Eifel. 



In the anthraciferous tract, the lower quartzo-schistous 

 system, referred pardy to the Llandeilo and Caradoc forma- 

 tion and partly to the Wenlock shale, is divided by M. Du- 

 mont into three stages : the lower, which contains no lime- 

 stone nor fossils, or at least the latter, are extremely rare; the 

 medial, in which the remains of organized bodies are also 

 very seldom exhibited ; and the upper, distinguished by the 

 abundance and variety of its Shells and Polyparia from all 

 other portions of the anthraciferous tract. In the upper 

 stage, nodules or beds of fossiliferous limestone are often con- 



Bruxelles, 1832, a work respecting which I agree with M. Beyrich, that it 

 does not appear to have drawn as much attention as it deserves. See the 

 same author also on the Ardennes, Belgium, &c., in the Bulletin de I'Acade- 

 mie Roycde des Sciences d J]riLvelles,]Sovemhev 1836 and November 1837. 

 * Elimens de Geologic, troisieme edition, 1839, pp. 476, 477- 

 f Terrain anthraxifere — this term, introduced in 1808, by M. d'Halloy, 

 is admitted by the author not to be good, since anthracite is found in oflier 

 groups, and it does not occur in all the systems which compose the tract 

 designated as anthraciferous by himself and JVI. Dwmont.—Elanens de Geo- 

 logic, third edition, p. 438. 



