REMAINS IN THE COAL-FORMATION OF NOYA SCOTIA. 
625 
After a quiet accumulation of vegetable matter, sufficient to give six inches of pure 
coal, the area must have subsided or been overflowed with water, probably brackish, in 
which Naiadites and Entomostracans established themselves, but in which for a time 
very little sediment was deposited, the dead plants remaining on the surface of the 
submerged swamp, and possibly others drifted to the locality, forming, with a little fine 
argillaceous matter, the material of carbonaceous shales. In the meantime the stronger 
and larger trunks of the Sigittaida forest remained erect, and around their bases there 
gradually accumulated layers of mud, constituting the shale, No. 10, including drifted 
plants, while it is not unlikely that the abundant remains of Splienojphyttum and 
Pinnularice represent aquatic vegetation growing on the surfaces of the accumulating 
mud. At this time the greater number of the trees had either not yet become hollow 
or were too tall to receive any sediment. A few, to be noticed in the sequel, were 
however either wholly or in part filled with clay. 
By gradual silting up, possibly aided by a slight elevation, the area again became 
capable of supporting land plants, as evidenced by the erect Catamites and Catamo- 
dendra which rise from the surface of the shale, and by the Stigmarice in the succeed¬ 
ing sandy deposit. The surface however now became subject to periodical or occasional 
inundations bearing sand, at first fine and argillaceous, but afterwards coarser. In the 
intervals of these inundations the thickets of Catamites and ferns which occupied the 
ground were tenanted by Batrachians, Millipedes, and Land Snails. 
In the meantime the larger and stronger Sigittarice, which had remained erect, 
while sand was accumulating around their trunks, became hollow through decay, the 
strong outer rind alone remaining, while the inner bark and woody axis fell to pieces 
and dropped into the bases of the hollow cylinders. In this condition these hollow 
trees would constitute deep wells and pits in the soil, their openings more or less 
masked with herbage or with shreds of bark projecting above the surface. They no 
doubt served as places of retreat to Millipedes and Land-Snails; but to the small 
reptiles heedlessly passing over the surface they were pitfalls into which they fell, and 
being unable to escape, perished. 
In connexion with this, it should be observed that the conditions of the case 
excluded all animals unable to creep or walk on land. Hence the assemblage of 
species in these trunks is of a special character, and includes none of those more 
aquatic forms of Batrachians which have been discovered in the aqueous deposits 
of the period. Further, only the smaller animals of the locality would be entrapped, 
larger species being little likely to fall into openings so narrow. 
How long any of the hollow trees remained open it is impossible to say ; but there 
is, as might be expected, evidence of successive stages and different modes in their 
filling. Some short bases of trees, resting on the coal and not extending into the 
shale, are mere disks of mineral charcoal, and may represent trees which had gone to 
decay even before the first submergence of the coal. Others seem to have been 
broken off before the close of the deposition of the shale, and are filled with that 
4 L 2 
