﻿2 GANOID FISHES OF THE CARBONIFEROUS FORMATION. 



James Armstrong, James Thomson, and John Young, of Glasgow, and Mr. Davies, of 

 the British Museum, for the liberality with which they have assisted me by affording me 

 facilities for the examination of specimens, in some cases belonging to themselves as 

 private collectors, in others under their charge as public officials. 



In indicating the stratigraphical occurrence of the various species to be described in 

 the present Monograph I shall follow the nomenclature applied to the subdivisions of the 

 Carboniferous strata of Great Britain used by Mr. Bristow in his ' Table of British 

 Strata/ The entire series of Carboniferous rocks may be grouped into two great 

 divisions, Upper and Lower. The Upper division, the great repository of coal and iron- 

 stone in England and Wales, constitutes the true " Coal Measures," and is throughout 

 the island singularly alike in its mineralogical and palaeontological characteristics. It 

 consists of a great series of sandstones, shales, and fireclays, with workable seams of coal 

 and clay-ironstone, in which typically marine fossils are comparatively rare, the strata 

 having apparently owed their origin to deposition under estuarine conditions extending 

 over a vast area, and in many cases obviously to the successive temporary submergence 

 of extensive low- lying tracts densely clothed with subaerial vegetation. The Lower 

 division, on the other hand, differs equally remarkably in its characters in different parts 

 of the United Kingdom, purely marine conditions having evidently prevailed in some 

 districts, while in others estuarine strata essentially similar to those of the Coal Measures 

 were being deposited. Thus, in England and Ireland the Lower Carboniferous rocks are 

 mainly represented by the well-known Carboniferous or " Mountain Limestone/' rich in 

 Brachiopoda and Corals, and in some places, as in Derbyshire, attaining an enormous 

 thickness ; while in Scotland, on the other hand, the purely marine beds are comparatively 

 thin, and occupy an entirely subordinate position in an immense mass of strata 

 containing land plants and seams of coal, and in general aspect closely resembling the 

 Coal Measures above. 



The subdivisions of the Carboniferous rocks of the southern parts of Great Britain 

 are given by Mr. Bristow as below : 



Upper 

 Carboniferous 



Lower 

 Carboniferous 



South Wales, fyc. 



rUpper 

 I n„„i 1 



Coal Measures. 

 Central Coal Measures 



or Pennant Grits. 

 Lower Coal Measures. 



-Millstone Grit. 



Upper Limestone Shale. 



| Carboniferous Limestone. 

 l^Lower Limestone Shales. 



Lancashire, Derbyshire, 

 and South Yorkshire. 



Upper Coal Measures. 

 Middle Coal Measures. 



Gannister Beds or Lower 

 Coal Measures. 



Millstone Grit. 



Limestone Shale or 

 Yoredale Rocks. 



Carboniferous Lime- 

 stone; no base. 



North Yorkshire, North- 

 umberland, and borders 

 of Cumberland. 



Upper Coal Measures. 

 Middle Coal Measures. 



Millstone Grit. 

 Yoredale Rocks. 



Carboniferous Limestone. 



