§21. ORGANIC REMAINS OF THE CARBONIFEROUS SYSTEM. 693 



numerous genera and species. The animal remains are 

 principally found in the calcareous and arenaceous strata, 

 and are referable to zoophytes, mollusca, radiaria, Crustacea, 

 and fishes : but few, if any, undoubted relics of any of the 

 higher orders have been discovered. The vegetable fossils, 

 besides constituting the entire mass of the coal, anthracite, 

 &c. are thickly interspersed in the shales, grits, and other 

 intervening deposits. The shells are almost exclusively 

 marine, but there are intercalations of fresh-water species 

 in some localities ; as, for example, in Coalbrook Dale, and 

 in the carboniferous beds at Burdie House, near Edin- 

 burgh, which consist of limestone and indurated clays, 

 with fresh-water shells, crustaceans, and sauroid fishes, 

 associated with terrestrial plants. These appear to be 

 interpolations between the marine deposits, and were pro- 

 bably formed in an estuary communicating with a river of 

 considerable extent.* In the coal measures of several 

 parts of the central counties of England, around Shrews- 

 bury for instance, there are likewise beds of fresh-water 

 limestones. 



But the grand features of the carboniferous system are 

 the immense accumulations of the early vegetation of our 

 globe, presenting to us, in the most legible and striking 

 characters, the peculiar flora of the remote epoch in which 

 these deposits were produced. To obtain any satisfactory 

 results from an examination of these remains, some know- 

 ledge of the internal structure of vegetables is requisite ; 

 for in a fossil state many of the external characters are, for 

 the most part, so imperfect or obliterated, as to afford but 

 obscure indications of the nature of the original. As in 

 our investigations of the fossil remains of animals, we 

 availed ourselves of the principles of comparative anatomy 

 to reconstruct those extinct forms of being, in like manner 



* Dr. Samuel Hibbert, " On the Fresh-water Limestones of Burdie 

 House, near Edinburgh." Edinb. Phil. Trans, vol. xiii. 

 z z 2 



