Chap. XVII.] 
DEVONIAN KOCKS OF FKANCE. 
411 
have been compared by de Verneuil with those of the lower shelly grauwack6 of the 
Ehine and the limestone of the Eifel ; and he has found that many of them are identical. 
Among these, the broad-winged Spirifer macropterus, Terebratula Archiaci, Grammysia 
Hamiltonensis, and Pleurodictyum problematicum are striking Devonian forms, un- 
known in any Upper Silurian rocks. The great number of species common to the 
limestones of La Sarthe *, and Nehou t in Normandy, and the lower fossiliferous band 
of the Ehine naturally leads to the belief that the French and Prussian formations are 
cotemporaneous. If this view be adopted, we must presume that France possesses no 
proper and full equivalent of the English Middle Devonian limestone, but simply the 
inferior portion of the group, called by Dumont the ' Systeme Ehenan,' and the upper 
member as seen in the Boulonnais. 
Having established the connexion between the Devonian rocks of the West of France 
and the lower portion of the group in the Ehenish Provinces, de Yerneuil observes that 
in such a consecutive development we might expect to meet with some species which on 
the continent of Europe and the British Isles are considered to be Silurian ; and such 
is the case. Thus Bronteus Brongniarti, Acroculia robusta, Terebratula eucharis, 
T. Haidingeri, Atrypa reticularis, Orthis Grervillei, Leptsena Bouei, L. Bohemica, and 
L. Phillipsi are found in the Devonian of France, and also in the uppermost Silurian 
of Bohemia. At the same time, Pentamerus galeatus, Atrypa reticularis, with the 
Corals Heliolites interstinctus, H. Murchisoni, Favosites fibrosus, and Chonophyllum 
perfoliatum, are common to the Upper Silurian of England or Sweden and the Lower 
Devonian of France. 
The Devonian group of Brittany and the West of France is also usually cur- 
tailed, like the Silurian, of its superior members — those which, in the Rhenish 
Provinces, are so fully developed between the above-mentioned rocks and the 
base of the Carboniferous system. There are, however, some exceptions. Re- 
cent researches have proved the existence of Upper Devonian in the vicinity of 
the anthracitic band of the Basse Loire, at a place called Copchoux. A young 
geologist, M. Bureau, has discovered there, in lumps of limestone, Rhynchonella 
cuboides, Rh. pugnus, Spirifer glaber, &c. % 
In the ' Bas Boulonnais ' also we meet with a fair representative of the Upper 
Devonian, rich in fossils, on which in 1840 § I published a short memoir. It 
is there immediately overlain by the Carboniferous Limestone ; and both of 
the formations extend into Belgium and the Rhenish Provinces, occupying the 
same relative position ||. This Upper Devonian is everywhere recognized by the 
abundance of its Spirifers, among which Sp. disjunctus, Sow. (Sp. Verneuilii, 
Murch.), and its numerous varieties are the most characteristic. Productus sub- 
aculeatus and Athyris concentrica are also frequently found. The limestone 
recurs in different bands with dolomites, sandstone, and schist, composing a 
* De Verneuil and Eouault, ante, p. 407. 
t At this locality abundance of Devonian fossils 
were obtained by the late M. de G-erville, and dis- 
tributed among his friends. Both Trilobites and 
Shells are found there ; and among the latter are 
the common Devonian species Cyrtina hetero- 
clita, Athyris concentrica, and Calceola sandalina. 
More than 45 species of Brachiopoda were found 
here by Mr. Davidson. 
I Bull. Soc.Ge'ol.de France, ser. 2. vol. xviii. p. 37. 
§ At that time the exact relations of the strata 
had not been determined, and I was deceived as 
to the nature of a small imperfect body, probably 
a Polyzoan, which was taken for a G-raptolite 
(Bull. Soc. Ge'ol. France, vol. xi. p. 229). M. Du- 
souich, who has published a good geological map 
of the Departement du Pas de Calais, and M. De- 
lanoue, who gave a small map of the Bas Boulon- 
nais, have ascertained by sinkings that the Devo- 
nian deposits range underground towards Be'thune 
and Arras (Bull. Soc. Geol. Fr. 2nd ser. vol. ix. 
p. 399). 
|| Mr. G-odwin-Austen, whose labours have 
thrown so much light on the real nature of the 
limestones of Devonshire, has surveyed this dis- 
trict of the Boulonnais in detail, and has endea- 
voured to show that its lowest strata (limestones, 
dolomite, &c.) represent the rocks of the Eifeh' 
and are charged with the same species of Corals, 
and many of the same Mollusks, which are so 
well known in Devonshire and on the Continent. 
His section does not exhibit any representative 
of the Spirifer- Sandstone or Lower Devonian of 
the Ehine ; but the rest of the Devonian rocks of 
the Ehine and Belgium have, according to his 
view, their equivalents in the North of France 
(Quart. Journ.G-eol. Soc. vol. ix. p. 231). This view, 
however, is not adopted by de Verneuil, de Ko- 
ninck, and others, who continue to view the chief 
masses of the Boulonnais as Upper Devonian. 
