123 
a regular succession of strata characterized by distinct fossils differ- 
ing more and more in descending order from the organic remains of 
the mountain limestone, and approaching those of the Silurian sy- 
stem; the authors proceed to enumerate the order of the groups and 
the imbedded fossils in South Devon and the North of Cornwall. 
They show a similarity of succession of deposits and of organic 
remains in the upper groups, but they state that in consequence of 
the protrusion of the granite, there is in the lower a considerable 
difference in mineral type, especially south of Dartmoor. They 
refer, however, to their former memoir for ample details respecting 
these counties, and for proofs that they were correct in placing the 
great calcareous masses of Plymouth and Chudleigh on the same 
parallel as the lowest calcareous strata of North Devon. 
In -conclusion, the authors show, that the variation in Devon- 
shire and Cornwall from the ordinary type of the old red sandstone 
in Herefordshire and adjoining counties, cannot be admitted as a 
valid argument against assigning the slates and sandstones of these 
counties to that system, because the variations in composition of 
other formations within limited areas is equally great. They show 
also that the absence of the true carboniferous limestone in Devon- 
shire cannot disprove their present classification, because in Western 
Pembrokeshire that limestone is wanting, and the coal measures 
rest on older formations. 
In consequence of mineral character being no longer indicative 
of age, and the term greywacke being lithologically applicable 
to beds of every class of rocks, and as Devonshire affords the 
best type of the fossils of this intermediate system, the authors 
propose to substitute the term Devonian for old red sandstone ; 
and they hope that the organic remains, discovered in that county, 
will enable continental geologists to detect in their own country, 
a system of strata hitherto supposed to be almost peculiar to the 
British Isles. 
‘The authors acknowledge the assistance they have received from 
Mr. J. Sowerby; and that Mr. Lonsdale first suggested, from their 
fossil contents, that the limestones of S. Devonshire might prove to 
be the representatives of the old red sandstone. 
A paper was afterwards read on the structure of South Devon, by 
Robert A. C. Austen, Esq., F.G.S. 
This communication is supplementary to a memoir read in 1837 *, 
and its object is to show the general relations of the various bands 
of slates, limestones, and sandstones in South Devon. 
Commencing with the older deposits east of the Teign, there ap- 
pear— 
Ist. Slates, but of which little is seen. 
2nd. A band of black stratified limestone of variable thickness 
and slaty structure. It contains much carbonaceous matter, thin 
seams of anthracite, also corals and Brachiopoda. It is associated 
with irregular beds of contemporaneoustrap. The band is stated to 
range from Staple Hill on the east, through Bickington, Ashburton, 
* Proceedings, vol. ii., p. 584. 
