Ixvi DESCRIPTIVE REMARKS. 
In Ireland the Lower Carboniferous slate and grits, except at par- 
ticular localities, contain but few fossil plants ; Anorrza like stems with 
simple branching torms, /v/icctes lineatus, are the prevailing kinds which 
have been hitherto noticed, 
The great central mass of Limestone is purely marine, and contains 
still fewer traces of vegetable remains; the intermediate shales occa- 
sionally display Fucoidal like forms and rarely anything like terrestrial 
plants. 
It is only when we arrive at the upper division, or Coal Measures, 
the superabundant remains of a primeval vegetation becomes apparent ; 
changes from a marine or estuary condition to that of a terrestrial one 
are observable in many of our Coal fields, such as that of Coalbrook- 
dale, where at least five decided alternations in the character of the 
strata from marine to terrestrial have been observed. In South Wales, 
where the Coal Measures are estimated to contain the great thickness 
of 12,060 feet, and 100 Coal beds are, it is said, intercalated at various 
levels, we have also positive evidence of alternating marine conditions; 
marine shells having been found associated with some of the lowest 
beds of coal.* Each of these Coal seams rests immediately upon a 
band of clay or sandy shale, called Underelay or Seat rock, which abounds 
with the plants called Stigmarza, or roots of Sigillaria, one of the most 
abundant plants in the Coal series, and one which must have contri- 
buted largely to the production of Coal. 
From this series of strata, principally in the shales immediately 
above and below the Coal seams, more than 300 different kinds of fossil 
plants have been described, belonging, for the most part, to the class of 
Cryptogamia, Ferns or Acrogens being the most prevalent. One of the 
most universally distributed of these is Alethopteris lonchitica, Plate 
xxxiv., fig. 2, a, b. Sphenopteris Heninghausit, fig. 3, a, b, is another 
abundant fern of a different character. A very important and numer- 
ous class of plants named Calamites, probably allied to the Kquesetacee, 
occur in profusion in almost every Coal field. Calamites canneeformis, 
fig. 1, being one of the most characteristic species. Lepidodendron 
Sternbergii, fig. 4, a, b, ¢, is considered to be allied to the Club Mosses, 
although of gigantic proportions, being referred with them to the 
Lycopodiacee. 
Another group of important Coal Plants are the Sigillariee, of these 
Sigillaria tessellata, fig. 5, a, b, showing trunk and roots St:gmaria ; 
the stumps of this plant often passes through the shale and coal, and its 
roots traverse the underclay. ‘These stumps, when unobserved by the 
workmen on excavating the coal which supported them, fall through, 
causing frequent accidents. They are locally termed Gell moulds, from 
their rounded extremity. 
The three last named genera contained plants, several of them of 
very large size, resembling in that respect some of our Forest Trees, 
* Bevan, Brit. Assoc., Rep. Trans. Sect., 1858, and Salter’s Appendix to the Iron 
Ores of S. Wales, Geol. Surv. Mem., 1861. 
