THE 
GEOLOGICAL MAGAZINE. 
NEW SERIES. DECADE II. VOL. VII. 
No. VIII—AUGUST, 1880. 
ORIGINAL ARTICLES. 
——>—__ 
I.—On tue Species or BracuropopA THAT OHARACTERIZE THE 
“Gres ARMORICAIN” OF BRITTANY, TOGETHER WITH A FEW 
OBSERVATIONS ON THE BuDLEIGH SALTERTON “ PEBBLES.” 
By Tuomas Davinson, F.R.S., F.G.S. 
(PLATE X.) 
URING the past twelve months I have devoted much time 
to the careful study of those questions that relate to the pro- 
bable source of derivation of the sandstone and quartzite boulders 
or “pebbles ” that were drifted and accumulated in the neighbourhood 
of Budleigh Salterton by “ Bunter” waters. The detailed results 
of my investigations will appear in my forthcoming Devonian Sup- 
plement. Cornwall and North Devon having been pointed at, as a 
probable source of derivation, I considered it necessary to study the 
rocks and fossils that exist in those portions of Great Britain, as 
well as those that occur in Normandy and Brittany, on the other 
side of the Channel. 
After some little trouble I was able to assemble, for examination, 
numerous examples of rock, and all the specimens and species of 
Brachiopoda that had been collected from the Lower Silurian 
deposits of the south of Cornwall, and which were kindly lent to 
me out of the museums of Penzance, Truro, the School of Mines, 
London, the Woodwardian Museum, Cambridge, the Museum of 
Edinburgh Geological Society, as well as from various other sources. 
Mr. Peach, the father of Cornish Lower Silurian geology, and first 
discoverer of its fossils, afforded me every facility and information 
within his power, as did also Mr. J. H. Collins, of Truro. 
After a long and careful examination of all these Cornish spe- 
cimens, and a lengthened correspondence upon the subject with 
M. de Tromelin, I found that they represented five species only, or 
that were identifiable, viz. Strophomena grandis, Orthis WScotica, 
Orthis calligramma, var. O. Berthosi, var. Cornubiensis, and O. 
Budleighensis (the shell so often confounded with Orthis redux, of 
Barrande).! I also examined with care the Devonian rocks of North 
1 I have devoted a quarto plate to the illustration of the Cornish species, and four 
to the delineation of those that occur at Budleigh Salterton, 
DECADE II.—vVOL. VII.—NO. VIII. 22 
