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The chief objects of the paper are to show, that the strata can be 
divided into certain groups, distinguished by well-marked lithologi- 
cal characters; and that there is a gradual passage from the lowest 
part of the uppermost or culm deposit into the series next below it, 
and that similar passages are presented in each of the other underly- 
ing groups. ‘To the intermediate strata the term neutral is applied. 
The whole of the beds are assigned to the transition or gray- 
wacke class, and are arranged in descending order under the fol- 
lowing nine heads, the topographical names being derived from the 
localities where the strata are best exposed :—9. Floriferous slates ; 
8. Coddon Hill grits; 7. Trilobite slates; 6. Wollacomb sand- 
stones; 5. Morte slates; 4. Trentishoe slates; 3. Calcareous slates 
of Linton; 2. Foreland and Dunkerry sandstone; 1. Cannington 
Park limestone. Only 9. 8. and 7. are described in the paper; the 
other six, confined, the author believes, to the north of Devonshire 
and the south of Somersetshire, being reserved for future consi- 
deration. 
9. Floriferous slates and sandstones.—This term 1s proposed for the 
series of beds containing culm, to avoid the ambiguity of the word 
** carbonaceous,” and as preferable, in the author's opinion, to 
*“‘ culmiferous,” plants being very generally distributed, and culm 
confined to a small area. The sandstones are finely micaceous, 
tough, externally of a rusty or dull purple colour, and internally of a 
dull olive, and they are stated to be totally distinct from any others 
in the country. The shales or slates are commonly dark-coloured 
and friable, but at Forrabury and Bos Castle they constitute roofing 
slates, resembling those of the inferior groups, though much dete- 
riorated by a combination of pyritous anthracite. One variety, called 
Adder Limestone, is a fine hone slate. The culm forms great insu- 
lated elliptical “‘ bunches,” sometimes gradually thinning out, and 
sometimes being suddenly nipped off. The strata are strangely 
contorted, and these disturbances have entailed on the country its 
physical features of rapidly succeeding hills and valleys; but Mr. 
Williams conceives, that the curvatures are confined to No. 9. 
and the two upper divisions of No. 8. and that they are due to 
lateral pressure produced by the upheaval of the granite of Dart- 
moor. ‘The area occupied by the “‘floriferous deposit” is stated 
to be 50 miles in a west and east direction, and 25 in a north and 
south. 
8. Coddon Hill Grits —On the confines of this formation the 
floriferous sandstones become thin-bedded and coarsely laminated, 
and after a series of alternations and gradual transitions, are finally 
succeeded by the well-characterized Coddon Hill grits. This series 
is divided by the author into grits, limestones, and dark slates, con- 
necting the floriferous sandstones (9.) with the trilobite slates (7.) ; 
and Mr. Williams asserts, that more regular passages from one 
system of beds to another cannot exist, there being no want of 
conformity, and that as the constituents of one deposit gradually 
decrease those of the other gradually increase. The grits are stated 
to be lithologically distinct from any other in the country. They 
