104 Transactions. 
strata, either of shell limestone, of argillacious limestone, thought 
from its fossils to be of fresh water or estuary origin. Unless in its 
fine white sandstone got in the neighbourhood of Edinburgh, and 
sent over the country for building purposes, in its fine grained 
estuary and shell limestones (Burdiehouse and Burntisland), and 
in the greater profusion of its shells and fishes, the lower 
group, as developed in Scotland, differs little in appearance from 
the upper group. Hence the term lower coal measures generally 
applied to itin this country. If we look at the lower coal measures 
in the mass there cannot be a doubt that they were laid down 
under very different conditions from the old red sandstone beneath 
and the mountain limestone above. Both of these formations are 
truly marine, the yellow sandstones being filled with true oceanic 
fishes, and the mountain limestone crowded with marine shells 
and corals. The lower coal measures, on the contrary, have more 
of a fresh water than of a salt water aspect. Coralloid corals are 
seldom obtained in their strata; their shells are mostly esturine ; 
their plants seem to have grown and flourished in marshes and 
delta jungles, and many of their fishes are large and of a saurial 
description. Under these circumstances, we may be quite 
safe in regarding it as a separate group. As a whole, 
the lower coal group in Scotland is eminently characterised 
by fresh water or estuary remains, though in several 
parts we may find seams of limestone and ironstone occur 
frequently, containing encrinal joints, retipora, palechinas, 
murchisonia, and others ; thus showing that during the laying 
down of the strata there were various alternations of marine and 
fresh water conditions. The plants of this group are much the 
same as those already before described. Of the animal remains 
the most characteristic are most minute crustaceous Cypris, Scoto- 
burdigatensis, and Hibbertii, which abound in all the limestones and 
shales. There are, however, frequent inter-stratifications of igneous 
rock and precipitated showers of volcanic ash, as if the seas and 
esturies of deposit had also been the seats of submarine volcanoes 
and craters of eruption. The iron which impregnated the waters 
of the old red period, and coloured with rusty red the whcle of 
that system, now appear in the segregated form of thin layers 
and seams of ironstone. At this point I think we might say a 
few words on some of the Dumfriesshire limestone quarries, which 
I visited some time ago, then possessed by the late Mr 
