68 
NOEMANDY, 
Miocene ” beds, and according to M. Bonissent it certainly 
underlies the “ marnes a Nassa.” In lithological character it 
is usually an agglutinated ferruginous gravel with rolled fossils, 
hard in some places, sandy in others. A clayey sand, with 
pebbles and rolled bones at its base, has been discovered by 
M. Yasseur near Gourbesville.* This sand has yielded a large 
number of fossils to the researches of MM. Yasseur and Dollfus, 
and is evidently of the same age as the conglomerate. Of 
143 species determined by M. Dollfust about 91 are known in 
the Coralline Crag, and only 53 in the Bed Crag; at least 85 of 
the species are still living in Europe, the per-centage of living 
Mollusca being identical with that found in the Coralline Crag. 
The Pliocene fauna of Normandy is so important for com¬ 
parison with that of the English Pliocene beds that a column is 
devoted to it in the tables at the end of this volume. The mol¬ 
lusca point to conditions very similar to those indicated by the 
shells from St. Erth, a large number of them being species found 
on a rocky bottom ; most of them indicate the lower part of the 
laminarian zone, but the truly littoral Patella is also represented. 
The sands seem therefore to point to slioaler water than the clays 
of St. Erth, for Gourbesville is not dominated by any high land, 
and we appear in this case to have the fauna that lived at the 
same depth as that in which the sands were deposited. 
The next division of the Pliocene series found in Cotentin is 
the Nassa marls of Saint-Martin-d’Aubigny. These marls 
M. Bonissent has seen restino: on the bed with Terehratula 
grandis. M. Dollfus describes the beds as consisting of greenish 
clav, having a thickness of 5 or 6 metres, and situated at 2 metres 
above the mean level of the sea. The most marked characteristic of 
the fauna of Bosq d’Aubigny, yielding 50 per cent, of living species, 
is its southern facies ; according to M. Dollfus, it is the upper Bed 
Crag of England, with 75 per cent, of Subapennine species. J If 
this deposit be truly of the age of the Bed Crag of England, and of 
the Scaldisian of Belgium, it is difficult to understand the markedly 
southern character of its fauna, while that of even the oldest 
portion of the Bed Crag is somewhat northern. It is also sur¬ 
prising to find a stratum containing only 50 per cent, of recent 
species overlying one containing as much as 60 per cent. Of 
course if the Straits of Dover did not yet exist, or were obliter¬ 
ated by a rise of land which cut off the English Channel from the 
North Sea, a considerable discrepancy in the temperature of the 
water might be thus accounted for. The general facies of the 
fauna, and the small per-centage of recent species would, how¬ 
ever, incline one to refer the Nassa marls to the older Pliocene 
period rather than to the newer Pliocene. The difference between 
the fossils of Gourbesville and those of the Nassa beds isunore 
suggestive of slightly varying conditions tlian of any great lapse 
* Bull. Soc. G6ol. France, ser. 3, vol. vii. p. 743. (1879.) 
t Esquisse de& Terrains Tertiaires, p. 520. 
j See also G. Dollfus, Essai sur I’Extension des Teri’ains Tertiaires dans le 
Bassin Anglo-Parisien, op. cit. p. 584-605. 
