510 Notices of Memoirs—W. H. Hudleston— 
Professor Hull as most striking. On the whole there still seems a 
little obscurity as to the details of the lowest Devonian beds on the 
Bristol Channel. 
There would be no use in considering the Tevouiae sequence in 
South Devon until that in North Devon had been fairly settled. It 
is not always that opportunities are afforded for studying a set of beds 
in duplicate within a limited distance, but I have had occasion to 
notice, more than once, the very great differences of development 
that present themselves under such circumstances within areas not 
so very far apart. Doubtless the original differences were very 
considerable, since South Devon must be regarded to a certain extent 
as a reef region, and the beds moreover were largely reinforced by 
contemporaneous volcanic matter of a basic nature, from which the 
equivalent beds in the North Devon area were almost entirely free. 
But in addition to these congenital elements of difference are others 
belonging to a subsequent period, such as a further extravasation of 
igneous rocks, and above all the extraordinary folding and com- 
pression to which the beds have been subjected. The confusion is 
something terrible, and we may regard the district as practically 
unmapped, although, thanks to Mr. Champernowne and others, a 
certain amount of correlation with the North Devon beds bas been 
established. 
The backbone of the system is constituted by the Great Devon and 
Plymouth limestones with their associated upper and lower slates, 
the upper or Dartmouth slates more especially corresponding with 
the Morte slates of North Devon. Underlying these central beds, 
or Middle Devonians, are the Torquay Grits, containing the Homalo- 
notus-beds, some of which struck Mr. Champernowne as being 
suspiciously like certain Ludlow rocks. These of course are naturally 
correlated with the Hangman Grits and Lynton Slates. Whether 
beds as low, or even lower than these, occur in any other part 
of South Devon, I am not in a position to state; but the beds of 
Yealmpton Creek have been placed on this horizon, and some 
geologists have even spoken of Silurian beds in the country north 
of Tavistock. On the other hand, the Upper Devonian, according 
to Mr. Champernowne, is represented by the Cockington Grits, 
originally described by De la Beche as Old-Red Sandstone, and 
these are the equivalents of the Pickwell-Down beds of North Devon. 
For Mr. Champernowne the Upper Devonian would appear to 
terminate with these beds, which he correlates with the Psammites 
du Condroz. Myr. Ussher, in describing the relations of the Devonian 
and Culm rocks on the east side of Dartmoor, observes that, as a 
rule, the Upper Devonian rocks occur in faulted association with 
the basement-beds of the Culm-measures. But in the area between 
Bovey Tracey and Bickington the uppermost Devonian beds are 
irregular slates, similar to the Pilton beds, and in one or two 
unfaulted junctions they pass up into Culm-measures, which are 
overlain by indurated shales of the Coddon Hill type. These recent 
observations of Mr. Ussher would seem to complete the anetey 
between the Devonian rocks in North and South Devon. 
