226 Proceedings of the Royal Physical Society. 
from their quantity and general distribution, may be regarded 
as characteristic of the series. 
Sigillaria, though represented by a number of species, is 
nowhere very common—the most frequently met with 
representatives of the genus being Stgillaria discophora, 
K6nig sp., and Sig. scutellata, Brongt. 
It is true that every one of these species occurs in the Middle 
Coal-Measures, and that all are even more or less common 
there; but in the Middle Coal-Measures they are associated 
with a great many other species, which are almost entirely 
unknown in the Lower Coal-Measures. 
The great distinguishing point then, between the Lower 
and Middle Coal-Measures, is not that the Lower Coal- 
Measures are characterised so much by a flora peculiar to 
itself, but by the absence of so many of the species which 
occur in the Middle Coal-Measures, and which give to this 
later series so distinguishing a character. 
It must be remarked, however, that the Lower Coal- 
Measures possess several species apparently peculiar to itself, 
such as Sphen. adiantoides, L. and H., Sphyropteris Boehmischt, 
Stur, Newropteris rectinervis, Kidston, Neur. Bliss, Lesqx., 
Neur. crenulata, Brongt., Stachannularia No rthumbriana, Kid- 
ston, Lepidodendron serpentigerum, Konig, Sigillaria Walchit, 
Sauveur, Psygmophyllum flabellatum, L. and H. sp., ete.; but all 
these are more or less rare, and several of them only known 
from one or two localities; and it is not so much on their 
presence that the distinguishing feature of the Lower Coal- 
Measure flora depends as on the absence of so many species 
that are common in the Middle Coal-Measures. 
Large tree-fern stems first appear in the Lower Coal- 
Measures, and are represented by Megaphyton Srondosum, 
Artis, and Megaphyton approzimatum, L. and ale They are, 
however, extremely rare. 
The flora of the Lower Coal-Measures, though — richer 
‘than that of the two series composing the Lower Carboni- 
ferous, did not attain to the same development as we 
meet with in the Middle Coal-Measures, where, perhaps, 
there is even a richer flora than that found in the Upper 
Coal-Measures. 
