202. | MR, A, J. JUKES-BROWNE ON pub 1902, 
the Black Shales, so as to make the thickness of oe latter appear 
less than it really is. 
The ‘ bone-bed,’ at the base of these shales, is not always to be 
seen; but Mr. Woodward’s notes describe it as consisting of one or 
two layers of black calcareous grit, containing small pebbles of 
quartz, with bones, teeth, and coprolites of fishes. Among them 
Gyrolepis Alberti, Saurichthys apicalis, Acrodus, Hybodus, and 
Lepidotus have been identified. 
Above the bone-bed are black shales, with some thin laminz of 
micaceous sandstone containing Pullastra arenicola; and still higher 
are shales with Avicula contorta, Protocardium rheticum, Pecien 
valoniensis, Anatina precursor, and impressions of Plewrophorus, 
Modiola, and other bivalves. 
Below the ‘ bone-bed,’ which is considered by some writers to be 
the base of the Rheetic Group, are the ‘ tea-green marls,’ which are 
now regarded by Mr. Woodward and others to belong to this group, 
and to be separable from the Keuper Marls. ‘These greenish-grey 
marls are well exposed, both at Charton Bay and at Culverhole Point; 
and, according to Mr. Woodward’s measurements, their thickness is 
from 30 to 34 feet. The highest bed is a greenish-grey calcareous. 
marl, which forms a thick band 9 or 10 feet thick. Below this are 
grey marls in regular beds, separated by seams of black marl and 
some layers of grey marly limestone; these have a combined thickness: 
of 12 or 14 feet. Below comes another band of greenish marl, 
8 feet thick, followed by 2 feet of grey marls with dark seams. 
No fossils have been found in these beds in Devon; but at 
Watchet, in Somerset, Pecten valoniensis, Protocardium rheeticum, 
and other fossils of Rhetic species have been recorded from 
them.’ The above-mentioned grey and black marls may be 
regarded as the base of the Rheetic Group, because no black shales 
occur lower down; but pale-grey and green marls, with hard 
caleareous bands, continue for about 18 feet, and terminate with 
a band of hard grey marl or marly stone: so that it is difficult 
to say which horizon should be taken as the better base. 
The Keuper Marls. 
If the lower of the two horizons above indicated be taken as the 
base of the Rhvetic, the highest beds of the Keuper, as seen in 
Charton Bay, consist of soft grey marls passing down into alter- 
nating beds of red and greenish marl. These beds are seen again 
at Culverhole, where they pass down into red and variegated marls, 
a considerable thickness of which is exposed in the lower part 
of Haven Cliff, east of the mouth of the River Axe. 
From Axmouth westward the Keuper Marls form the substratum 
of the whole country bordering the coast-line, as far as the valley of 
the Sid; and they are exposed in the lower part of the cliffs, for the 
greater part of the distance between Haven Cliff and Sidmouth. 
West of Seaton a cliff of red marl, which in places is somewhat 
+ W. Boyd Dawkins, in Quart. Journ. Geol. Soc. vol. xx (1864) p. 396. 
