742 



THE WONDERS OF GEOLOGY. Lect. VII. 



Carcharopsis. — By this name M. Agassiz distinguishes 

 a fish of the shark family, resembling the Carchariodonts 

 (Medals, p. 621, fig. 3), of which teeth have been found in 

 the carboniferous deposits of Yorkshire and Armagh in 

 Ireland. These teeth are compressed, triangular, and 

 crenated on the edges, with large plaits or folds on the 

 enamelled surface towards the base of the crown. These 

 are the only relics of fishes belonging to this tribe of 

 sharks, that have been discovered in strata below the 

 tertiary. 



48. Reptiles of the Carboniferous epoch. — Allu- 

 sion has already been made to the quadrupedal footprints 

 supposed to be those of batrachians, on argillaceous sand- 

 stone, low down in the coal measures of Pennsylvania. The 

 specimens collected by Mr. Lyell, and now in his possession, 

 appear to me undoubted impressions of this kind (ante, 

 p. 566). Other examples have been obtained from the same 

 place by Dr. King and other American geologists. These, 

 and the recent discovery of a considerable portion of the 

 skeleton of a saurian reptile in the coal strata of Saar- 

 briick, afford the most ancient indications of the existence 

 of any terrestrial vertebrated animals : and they are like- 

 wise the sole vestiges of any creature that crawled or 

 walked upon the surface of the lands that were clothed 

 with the luxuriant vegetation of the carboniferous flora. 



49. Climate of the Palaeozoic ages. — The cause of 

 the difference between the natural climates now prevailing 

 over extensive zones of the earth's surface, and those which 

 the organic remains discovered in the strata lead us to 

 conclude have formerly subsisted during very long periods 

 of time — and apparently over the greater part of its whole 

 extent — is one of those geological problems, the solution of 

 which is not at present within our reach. Unable to 

 account for so extraordinary a distribution of a high clima- 

 torial temperature — a diffusion of heat and light so 



