AIR-BREATHERS OE THE COAL. 
413 
gerathia^ etc., for genus, see Fig. 428, p. 393), supposed by 
Dawson to have been deciduous, and which had broad par¬ 
allel veined leaves without a mid-rib. On the surface of the 
seams of coal are large quantities of mineral charcoal, which 
doubtless consist, as Dr. Dawson suggests, of fragments of 
wood which decayed in the open air, as would naturally be 
expected in swamps where so many erect trees were pre¬ 
served. Beds of cannel-coal display, says Dr. Dawson, such 
a microscopical structure and chemical composition as shows 
them to have been of the nature of fine vegetable mud such 
as accumulates in the shallow ponds of modern swamps. 
The underclays are loamy soils, which n^ust have been suffi¬ 
ciently above water to admit of drainage, and the absence 
of sulphurets, and the occurrence of carbonate of iron in 
them, prove that when they existed as soils, rain-water, and 
not sea-water, percolated them. With the exception, per¬ 
haps, of Asterophyllites (see Fig. 461, p. 425), there is a re¬ 
markable absence from the coal-measures of any form of veg¬ 
etation properly aquatic, the true coal being a sub-aerial ac¬ 
cumulation in soil that was wet and swampy but not per¬ 
manently submerged. 
Air-breathers of the Coal. —If we have rightly interpreted 
the evidence of the former existence at more than eighty dif¬ 
ferent levels of forests of trees, some of them of vast extent, 
and which lasted for ages, giving rise to a great accumula¬ 
tion of vegetable matter, it is natural to ask whether there 
were not many air-breathing inhabitants of these same re¬ 
gions. As yet no remains of mammalia or birds have been 
found, a negative character common at present to all the 
Palaeozoic formations; but in 1852 the osseous remains of a 
reptile, the first ever met with in the carboniferous strata of 
the American continent, were found by Dr. Dawson and my¬ 
self We detected them in the interior of one of the erect 
Sigillariae before alluded to as of such frequent occurrence in 
Nova Scotia. The tree was about two feet in diameter, and 
consisted of an external cylinder of bark, converted into coal, 
and an internal stony axis of black sandstone, or rather mud 
and sand stained black by carbonaceous matter, and cement¬ 
ed together with fragments of wood into a rock. These frag¬ 
ments were in the state of charcoal, and seem to have fallen 
to the bottom of the hollow tree while it was rotting away. 
The skull, jaws, and vertebrae of a reptile, probably about 21- 
feet in length {Dendrerpeton Acadianum^ Owen), were scat¬ 
tered through this stony matrix. The shell, also, of a Pupa 
(see Fig. 442, p. 415), the first land-shell ever met with in the 
coal or in beds older than the tertiary, was observed in the 
