Ww. A. E. USSHER ON THE TRIASSIC ROCKS OF NORMANDY. 245 
20. On the Triasstc Rocks of Normanpy and their ENVIRONMENTS. 
By W. A. E. Ussuzr, Esq., F.G.S. (Read May 22, 1878.) 
INTRODUCTION. 
Mr. Vicary’s indefatigable zeal in the collection of specimens has 
attracted much attention to the lithological characters and fossil 
contents of the Budleigh pebbles. Being so different from those 
exhibited by Devonshire rocks (within the present limits of the 
country), the attention of geologists was divided between certain 
quartzites on the south coast of Cornwall, at the instigation of Mr. 
Peach, and the Grés de May, advocated by Mr. Salter, as the pro- 
bable source of the pebbles. Mr. Davidson, however, subsequently 
pointed out the preponderance of Devonian forms in the pebbles ; 
with his arguments and the inferences therefrom deduced I have 
dealt elsewhere*. It suffices here merely to state that the settle- 
ment of this vexed question induced me to spend part of my vacation 
in Normandy, after a careful perusal of M. Bonissent’s excellent 
and exhaustive memoir on the Geology of La Manchey; and that, 
from a footnote to Mr. Salter’s paper citing Mr. Godwin-Austen as 
to the occurrence of a similar Triassic quartzite gravel in Normandy, 
and from the personal observations of my friend Mr. Linford to the 
same effect, | was under the impression that the Norman area not 
only formed the south-eastern margin of our Devonshire Triassic 
basin, but that it would also furnish a sequence of deposits equi- 
valent to the Upper and Lower Keuper of Devon, and, owing to 
the proximity of quartzite rocks, would probably afford a much 
greater development of the quartzite gravels which heralded the 
formation of the Keuper in South Devon. 
M. Bonissent is dead, as I learned on my arrival at Carentan, so 
that I was unable to obtain any assistance in the investigation ; 
and this was the more distressing as I am compelled on general 
grounds to dispute a very material observation made by him as to 
the occurrence of Grés bigarré (bunter) at Montebourg. Limited 
time made my own observations so imperfect that I should have 
hesitated to question any assertion made by M. Bonissent, were it 
not that in this instance the absence of any corroborative statement 
renders the matter an open question for solution. 
In the following pages I shall have occasion frequently to quote 
M. Bonissent’s work, which remains a marvel of persevering energy, 
close observation, and exhaustive detail. Nor is it extraordinary 
that amidst so vast a field of labour, the fragmentary exposures of 
the Triassic rocks of La Manche should be relegated to so small a 
space as six pages (pp. 267-272). What I shall endeavour to prove 
* Trans. Dev. Assoc. for. 1877, p. 224. 
_ Tt “Essai Géologique sur le Département de La Manche.” Extrait des Mé- 
moires de la Société des Sciences Naturelles de Cherbourg et d’Avranches, 
Q.J.G.8. No. 138. 8 
