Chap. XVII.] 
PALAEOZOIC EOCKS OF BEITTANY. 
407 
the presence of Amplexus and Productus. Now, d'Archiac and de Yer- 
neuil have demonstrated that this highest group is neither Silurian nor 
Devonian, but a true member of the Carboniferous rocks. It is, in its 
fossils, identical with the Carboniferous Limestone of many regions. 
All these fossiliferous deposits, whether Lower Silurian, Devonian, or 
Lower Carboniferous, are conformably arranged, whatever may be the 
inclination of the beds ; and, striking from east 15° south to west 15° 
north, they overlap transgressively the older unfossiliferous rocks on which 
they repose. It was the accordance in their direction and inclination 
which naturally led Elie de Beaumont and Dufrenoy to include, in the first 
instance, all these fossiliferous deposits in one period. But in the interval 
which has elapsed since that classification was proposed, Brittany has 
been examined by many geologists, including Frappoli, de Fourcy, Du- 
rocher, Blavier, and Rouault, as well as by de Yerneuil and d'Archiac, all 
of whom agree in adopting the order and nomenclature here followed. 
The eastern limits of the province, towards the Departments of La May- 
enne and La Sarthe, have indeed been studied in the greatest detail by 
M. Triger, to whom the execution of the geological map of the last- 
mentioned district was confided. The collection of fossils made from the 
Palaeozoic rocks around Cherbourg by my old and indefatigable corre- 
spondent, the late M. de Gerville, has also contributed essentially to clear 
away the difficulties attending a right classification ; and, lastly, the Geo- 
logical Society of France (during its meeting at Le Mans, 1850), under 
the leadership of M. Triger, made a section across the older rocks to the 
north of Angers, the resume of which was published by de Yerneuil and 
de Loriere *. 
The following diagram (p. 408), reduced from their publication, exhibits the 
principal geological features of the country between Sille le Guillaume and Sable, 
a distance of about twenty-five English miles, and clearly developes a succession 
of the Palaeozoic formations from the Lower Silurian to the Carboniferous rocks 
inclusive. 
In this section, the lowest stratum is a white sandstone (1), resting on a por- 
phyry with large red and white crystals. The still more ancient crystalline and 
glossy schists of Brittany are here wanting ; whilst the lowest visible beds (1 to 
6), in which some limestone appears, have not yet afforded any fossils to serve 
as equivalents to those of the ' Primordial Zone ' of Bohemia and Scandinavia, 
or the Lingula-flags of Britain. 
Such was our knowledge when the last edition of this work appeared ; but 
since then some traces of what has been referred to the 'Primordial' Silurian 
fauna in France have been detected. Near St. Leonhard des Bois (Sarthe), 
MM. Triger and de Verneuil have discovered, under a mass of roofing-slates 
containing the Asaphus and Illaenus of Llandeilo age, beds of quartzose sand- 
stone, one of which was loaded with Lingulse and Bilobites, and they think it 
may be the equivalent of the Lingula-flags. M. Dalimier also regards the 
* In a recent excursion, MM. Triger, Daubrde, and de Verneuil discovered that this section is not 
so simple as it appeared to be in a former examination ; but the foldings of the strata do not affect 
the general order of succession here given. 
