PREFACE TO THE FIFTH EDITION. Vll 



late Professor E. Forbes, p. 294. Many new figures of fossils cbavacter- 

 istic of the subdivisions of the three Purbecks are introduced ; and the 

 discovery, in 1854, of a new mammifer alluded to, p. 295. 



Representations also of fossils of the Upper, Middle, and Lower Oolite, 

 and of the Lias, are added to those before given. 



Chap. XXIL — XXIIL — On the Triassic and Permian formations. 

 The improvements consist chiefly of new illustrations of fossil remains. 



Chap. XXIV. — XXV. — Treating of the Carboniferous group, I have 

 mentioned the subdivisions now generally adopted for the classification of 

 the Irish strata (p. 359), and I have added new figures of fossil plants to 

 explain, among other topics, the botanical characters of Calamites, Stern- 

 bergia, and Trigonocarpum, and their relation to Coniferse (pp. 364, 365, 

 368). The grade also of the Coniferae in the vegetable kingdom, and 

 whether they hold a high or a low position among flowering plants, is dis- 

 cussed with reference to the opinions of several of the most eminent 

 living botanists ; and the bearing of these views on the theory of progres- 

 sive development, p. 370. 



The casts of rain-prints in coal-shale are represented in several wood- 

 cuts as illustrative of the nature and humidity of the carboniferous 

 atmosphere, p. 381. The causes also of the purity of many seams of 

 coal, p. 382, and the probable length of time which v/as required to 

 allow the solid matter of certain coal-fields to accumulate, p. 383, are 

 discussed for the first time. 



Figures are given of Crustaceans and Insects from the Coal, pp. 

 385, 386 ; and the discovery of some new Reptiles is alluded to, p. 401. 



I have also alluded to the causes of the rarity of vertebrate and inver- 

 tebrate air-breathers in the coal, p. 401. 



That division of this same chapter (Chap. XXV.) which relates to the 

 Mountain Limestone has been also enlarged by figures of new fossils, and 

 among others by representations of Corals of the Paleozoic, as distin- 

 guishable from those of the Xeozoic, type, p. 403 ; also by woodcuts o^ 

 several genera of shells which retain the patterns of their original colors, 

 p. 406. The foreign equivalents of the Mountain Limestone are also 

 alluded to, p. 409. 



Chap. XXVI. — In speaking of the Old Red Sandstone, or Devonian 

 Group, the evidence of the occurrence of the skeleton of a Reptile and 

 the footprints of a Chelonian in that series are reconsidered, p. 412. 

 New plants found in Ireland in this formation are figured, p. 414 ; also 

 the Pterygotus, or large crustacean of Forfarshire, p. 415 ; and, lastly, the 

 division of the Devonian series in Xorth Devon into Upper, Middle, and 

 Lower, p. 420, the fossils of the same (p. 421 et seq.), and the equivalents 

 of the Devonian beds in Russia and the United States, are treated of, 

 p. 425 and 428. 



Chap. XXVII. — The classification and nomenclature of the Silurian 

 rocks of Great Britain, the Continent of Europe, and North America, ?,nd 

 the question whether they can be distinguished from the Cambrian, and 



