B04 STRATIGRAPHICAL GEOLOGY. [Boos VI. 
In the west of Scotland also relics of the same type of Cretaceous — 
formations have been preserved under the volcanic plateaux of Mull 
and Morven. ‘They contain the following subdivisions in descending 
order :* 
White marly and sandy beds with thin seams of lignite ...........-. 20 feet 
Hard white chalk with Belemnitella mucronata, &C.........0eeeeaee 10**,, 
Thick white sandstones with carbonaceous matter................. 100"..g 
Glauconitic sands and shelly limestones, Pecten asper, Hxogqyra conica, ; 
Janira quinquecostata, Nautilus deslongchampsianus, &e. ........+ 60); 
France and Belgium.’—The Cretaceous system so extensively deve- 
loped in western Hurope is distributed in large basins, which, on the 
whole, correspond with those of the chief rivers. Thus in France there 
are the basins of the Seine or of Paris, of the Loire or of Touraine, of the 
Rhone or of Provence, and of the Garonne or of Aquitania, including ~ 
all the area up to the slopes of the Pyrenees. In most cases these areas 
present such lithological and paleontological differences in their Cre- 
taceous rocks as to indicate that they may have been to some extent 
even in Cretaceous times distinct basins of deposit. 
Neocomian®—A. threefold subdivision of this series of deposits has 
been traced both in the Paris basin and in the southern provinces. The 
lowest group, in Marne, Haute Marne, Meuse, &c., consists of sands, 
marls, spatangus-limestene with Spatangus, Toaster complanatus, Perna 
Mulletii, and oyster-clays (Ostrea Leymerie:). In the south and east of 
France it assumes much greater dimensions and consists mainly of lime- 
stones, which towards the base contain Terebratula diphya (janitor, see ante, 
p- 800), Anmonites macilentus, in their middle portions Belemmites dilatatus, 
Ostrea Couloni, Spatangus, and in their higher zones Towaster complanatus. 
The middle group, or “‘ Urgonien” of D’Orbigny, consists of fresh-water 
clays, sands, and ironstones in the northern area, but in the south 
expands into a massive series of limestones with Chama (Caprotina) am- 
monia, Requienia (Caprotina) Lonsdalen, Pteroceras pelagi, Panopzea irregu- 
laris, Terebratula sella. 'The upper group, or “ Aptien ” of D’Orbigny, is 
composed in the Paris basin of plicatula-clays, with Ostrea aquila, Plica- 
tula placunea, Exogyra sinuata, Rhynchonella lata, Ancyloceras matheronianum, 
Ammonites fissicostatus, A. nisus, and in Haute Marne contains fresh-water 
beds with Paludina, Cyclas, &c.; in the Mediterranean basin it consists of 
marls (Marnes aptiennes) and sandstones, with similar fossils. In the 
1 Judd, Q. J. Geol. Soc. xxxiv. p. 736. 
* The Cretaceous system has been the subject of prolonged study by the geologists 
of France, and has given rise to considerable differences of nomenclature. The main 
formations recognized and named by D’Orbigny have been generally adopted. But 
great diversity of opinion exists as to the names and limits of the lesser groups. There 
has been a tendency to excessive elaboration of subdivisions, as may be seen in the 
classification proposed by M. Coquand. ‘The minor sections of the geological record 
must always be of but local significance, and it is to be regretted when they are treated 
as of any higher importance. M. Hébert has wisely refrained from burdening geological 
nomenclature with a long list of new names for local developments of strata, contenting 
himself with employing D’Orbigny’s names for the formations, and subdividing these 
into upper, middle, and lower. ‘The student will find some of the rival systems of classi- 
fication collected by Mr. Davidson, Geol. Mag. vi. (1869). 
® See D’Archiac, Mém, Soc. Géol. France, 2e sér. ii. p. 1; Raulin, Op. cit. p. 219; 
Ebray, Bull. Soc. Géol. France, 2e sér. xvi. p. 213; xix. p. 184; Cornuel, Bull. Soc. Geol. 
France, 2e sér, xvii. p. 742; 3e sér. ii, p. 371; Hébert, Op. cit. 2e sér. xxiv. p. 323; 
xxviii. p. 137; xxix. p. 894; Coquand, Op. cit. xxiii. p. 561; Rouville, Op. cit. xxix. 
p. 723; Bleicher, Op. cit. 8e sér. i. p. 21; 'Toucas, Op. cit. iv. p. 315. 
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