432 
THE CRETACEOUS ROCKS OF BRITAIN. 
CHAPTER XXXIV. 
THE MIDDLE CHALK OF THE DEVONSHIRE COAST. 
General Description. 
The outlying patches of Chalk which are intersected by the coast¬ 
line of Devonshire include a considerable thickness of Middle Chalk. 
The fine cliffs of Pinhay and Whitlands, and the still bolder walls 
of Beer Head, consist almost entirely of this Turonian Chalk, for, 
as stated on p. 126, the representative of the Lower Chalk is inmost 
places only a few feet thick. The Middle Chalk, on the other hand, 
is well developed and is actually, thicker than it is in the west of 
Dorset, having near Beer a thickness of 140 feet. 
The Zone of Rhynchonella Guvieri varies much in thickness, being 
between 50 and 60 feet near Lyme Regis and 35 at Beer Harbour, 
thinning to only 15 at Beer Head and disappearing altogether 
for a space in Hooken Cliffs, where the Terebratulina zone 
rests directly on the coarse sandstone of the lowest Cenomanian 
stratum. The lower zone comes in again to the westward, how¬ 
ever, and in Berry Cliff it regains a thickness of 38 feet. At Duns- 
combe it forms the most westerly patch of chalk in England. 
There is no regular bed of Mel bourn Rock at the base of the zone, 
the lowest bed being everywhere a hard, rough, gritty limestone 
containing grains of quartz and glauconite, but above this there is 
generally a bed of chalk full of hard yellowish nodules like those 
in Melbourn Rock. It is probably the equivalent of that rock in 
a looser and less consolidated form. 
The Beer Stone is a local development of shelly chalk in this zone. 
Mr. Whitaker was the first to describe it as actually part of the 
Chalk, and Dr. Ch. Barrois was the first to recognise its true zonal 
position. 
It is a remarkable fact that Micrasters are not uncommon in 
this zone in Devonshire, and Dr. Rowe informs me that both 
M. corbovis and M. Leslcei are present. 
The Terebratulina Zone.— This is the “Chalk with flints” 
of earlier writers and was supposed to be Upper Chalk simply 
because the flints are like those in the Upper Chalk ; they are very 
numerous, occurring both in layers and as scattered nodules. The 
fossils, however, are quite decisive as to its true stratigraphical 
position, which was first recognised bv Prof. Ch. Barrois in 1876.* 
It is a remarkable fact that this zone is thicker in Devon 
than it is in South or West Dorset, being near Beer about 80 feet 
thick and about 100 feet at Beer Head. 
*Recherches sur le Terrain Cretace Superieur, p. 72. 
