MIDDLE CHALK—-CONDITIONS OF DEPOSIT. 54P> 
the Cote d’Or. He says : “ The existence of Micrasters in flints 
at several places on the Morvan [Nievre] shows that the chalk 
was deposited over at least a part of this region, and that it has 
been removed by denudation. But were such testimony absent 
the same inference might be deduced from the great purity of the 
chalk along the south-eastern border, for it is in this part of the 
Paris basin that the formation best maintains its character of 
a pelagic deposit. We must admit the existence, not of a mere 
strait, but of a communication as wide as the whole region which 
now separates the Vosges from Morvan. Some patches of white 
chalk have been found at the foot of the Chalonnais slope, their 
preservation being due to faults. . . . White chalk, with 
Eckinoconus conicus and Micrasters, has been found near Lains 
(canton de Lons-le-Saulnier, Jura) at a height of 520 metres 
(1,700 feet), and even further south on the line of the Alpine chain. 
Our knowledge of the Cretaceous strata of Savoy, of Dauphine, 
of Haute Provence, and of the Alps affords abundant proof that 
it was in this direction that the Cretaceous Sea was prolonged, 
and not down the valley of the Phone.”* 
That a communication existed between the south-eastern part 
of the Paris basin and the Aquitanian region is also accepted by 
M. Cayeux, who speaks of it as the Strait of Poitou, and considers 
that it was by this passage that some of the Rudistce of the Hip- 
purite Sea gained access to the more northern parts of the 
Turonian Sea (Op. cit. p. 599.) f 
It is clear, therefore, that there is plenty of evidence for com¬ 
munications with eastern and southern seas ; it remains for us 
to consider the possibility of westward openings into an Atlantic 
Ocean. In the first place, we have no assurance that any such ocean 
existed in the Cretaceous period. Those who believe in the per¬ 
manence of oceans and continents consider, of course, that there 
was always an Atlantic Ocean from the earliest times to the present 
day, but this belief is founded upon theoretical conceptions of 
the manner in which the consolidation of the earth has been accom¬ 
plished, and is not accepted by all geologists. My own belief is 
that the oceanic depressions and the continental plateaux have 
been gradually developed through a long series of geographical 
mutations, { and that their present aspect is probably widely 
different from that which they presented in the Cretaceous period. 
Inasmuch as the greater part of Europe was unquestionably 
not continental land in Turonian and Senonian times, but was 
the site of a large sea or small ocean, studded with islands, it 
*He holds that Dr. Hume’s sketch-map was incorrect in showing a gulf 
running southward down the valley of the Bhone, but I see no reason why 
there should not have been an opening southward into the Hippurite Sea, 
as well as eastward into the Alpine Sea. The land in central France may 
have been an island. 
t See also de Grossouvre “ Sur le Detroit de Poitiers,” in Comptes- 
ren dus de 1’Assoc. Franc, pour l’Adv. des Sciences, 1901, p. 398. 
+ See Building of the British Isles, Second Edition, Chapter xvi. (1892), 
