Correspondence. 569 
The next system, in descending order, is the DEVONIAN, which in - 
North-eastern America is unconformable to the Carboniferous, and 
contains a totally different series of plants. Dr. Dawson has observed 
and catalogued about 82 species from these rocks in New Brunswick, 
and only ten of them can be identified, but doubtfully, with Car- 
boniferous forms; perhaps the Lower Coal Formation may be 
regarded as in some degree a transition group distinguishable from 
the Devonian Flora below and the Carboniferous above. The 
whole Devonian Flora appears to be one; for though only two of 
the Upper Devonian species can with certainty be referred to the 
Lower Devonian, yet these are two of its characteristic species. 
The Lower Helderberg Formation is the only part of the UPPER 
SinuRiAN Groupe that has hitherto afforded land-plants, and at only 
one locality, Gaspé, and here there appears to be a gradual passage 
from the Upper Silurian Limestones into the Lower Devonian Sand- 
stones; these plant-remains are the markings of the rhizomes of 
Psilophyton, and leaf-like impressions doubtfully referred to the 
Lower Devonian Cordaites angustifolia. 
Dr. Dawson notices the fact that the earliest known traces of 
land-plants occur in rocks of a similar horizon, both in Britain and 
America; he regards many of the so-called fucoids of the Lower 
Silurian Rocks of Canada as merely worm-burrows, trails of crusta- 
ceans or molluscs, shrinkage cracks, or concretions, some few, how- 
ever, are undoubtedly alge ; he has been unable to discover in any 
of the Lower Silurian forms the structure of land-plants, not even 
in the Potsdam Sandstone, which containing littoral deposits would 
thus seem to indicate a paucity in the land-vegetation of the period. 
He also states that though he has not at present succeeded in recog- 
nising any determinate forms in the graphitic matter of the Lau- 
rentian rocks, which presents the appearance of comminuted remains 
of alge, yet he entertains the hope of doing so. 
CORRESPONDENCE. 
—— 
ON THE NORTH STAFFORDSHIRE COAL-FIELD. 
To the Editors of the GEoLocicaL MaGaZzIne. 
Srr,—In the paper which Mr. Molyneux read before the Geo- 
logical Section of the last meeting of the British Association in 
Birmingham, he referred to a bed of greyish shales, lying a few feet 
above the Gin Mine Coal and belonging to the upper part of the 
low or thick measures of the North Staffordshire Coal-field. These 
shales, he justly remarks, surpass the Bog Mine in the number and 
variety of their organic contents. As you were informed by him- 
self, Mr. Ward, of Longton, had previously found beds of true 
marine shells in these measures. But the shales referred by Mr. 
Molyneux, as being sunk through, last June and July, were first 
noticed by a young man in this town of the name of Amison, who 
obtained from them, not only the fossils named in the above paper, 
but several others. Among the rest was a very large Nautilus ; 
