153 
He conceives they were originally swampy islands, formed out of 
disjointed fragments which resulted from the first elevation of the 
rocks ; that on these islands grew a luxuriant vegetation consisting 
of Ferns, Calamites, coniferous trees, &c. which, decaying and rege- 
nerating, accumulated in the manner of peat bogs; that the islands, 
by the settling down of the disturbed crust of the earth, were de- 
pressed beneath the surface of the sea, and covered over with drifted 
sand, clay, and shells, till they were again, by this process, converted 
into dry land, and clothed with another vegetation ; and he is of opi- 
nion, that the operation was repeated as many times as there are al- 
ternations of coal and sedimentary strata. 
A notice on the Fossil Fishes of the Yorkshire and Lancashire Coal- 
fields, by W. C. Williamson, Esq., was then read. 
About four years ago, Mr. Williamson first met with remains of 
fishes in the coal-measures of Lancashire. Nearly at the same time 
Sir Philip Grey Egerton detected them in the Staffordshire fields ; 
Mr. Hutton had previously found them near Newcastle ; Dr. Hibbert 
Ware had brought them before the public in Scotland; Mr. Bow- 
man had detected scales of Holoptychus in Wales; and two or three 
instances had been noticed of their existence in the coal-fields of 
Yorkshire. Since that period, however, the coal-measures of Lan- 
cashire and Yorkshire have proved to be exceedingly rich in Ich- 
thyolites. In the former, they occur throughout the whole series 
from the Ardwick limestone to the millstone grit; and at Middleton 
colliery, near Leeds, they have also been found in considerable quan- 
tity. At that locality there are three seams of coal, but only two are 
wrought. The following is a general section of the pits :-— 
isheoalys 8 save te ceae 14 inches. 
fntervall 2 ea OOl yards 
Mardi coal me cate ie alias 3 feet. 
Intenvallernti/cmenn: 32 yards 
Marmicodl aati at eran antec. 
Ichthyolites occur in the shale in connexion with all the seams, 
but principally in the uppermost one, to which the colliers have in 
consequence given the name of Fish Coal. They are contained in a 
fine bituminous shale, and in greatest abundance at the junction 
of the roof with the coal, where a very thin seam of coprolitic mat- 
ter occurs. ‘The author has obtained from it the following re- 
mains :— 
Teeth of Diplodus gibbosus and Ctenoptychus pectinatus; scales, 
jaws, and teeth of Megalicthys Hibbertii, and of another smaller spe- 
cies; rays of Gyracanthus formosus ; scales, fins, and other portions 
of two species of Holoptychus, of a species of Acanthodes, or Chei- 
racanthus ? and of a species of Platysomus; also three kinds of Ich- 
thyodorulites, and other remains of which he has not yet determined 
the genera. 
In the shale of the main coal Ichthyolites are much less abun- 
dant, but they are remarkable for their great size. They occur ina 
