On the Structure and 115 



fossils have been made, but not a trace of Edestus has been 

 found there. Hence we must infer that it never passed the 

 highlands of tlie Cincinnati arch, which separated the western 

 from the eastern coal basins. 



The material in which the spines of Edestus ai-e found, is al- 

 most without exception the bituminous shale which occurs so 

 frequently interst rati tied with the other elements of the coal 

 measures, and veiy frequently resting upon coal. 



From the black shale which forms the roof of a coal-mine at 

 Belleville, Illinois, ^fr. Alexander Butters, the superintendent 

 of this mine, has taken hundreds of the segments wliich once 

 composed the spines of E. Heinrichsii. This shale is apparently 

 a fresh-water sediment, carbonaceous mud which accumulated 

 in the lagoons of water that occupied portions of the coal 

 marshes ; eithei- following a subsidence, and then covering the 

 coal, or synchronous with the peat from which the cubical coal 

 is derived. In the latter case, the amount of earthy matter as- 

 sociated with the carbon is less, and we then have cannel coal. 

 Some of these lagoons must have been of large size, and may 

 perhaps have commuicated with the ocean, for the fishes which 

 bore these defensive and offensive weapons were of enormous 

 size, and could not have been lestricted to very narrow quarters, 

 since they required a vast amount of food for their subsistence.* 

 The associated fossils include a large number of fish-teeth, some 

 of which belonged to carnivorous sharks, as Cladodus and Petal- 

 odus, and others with crushing teeth as Orodus, Ortho2oleurodus, 

 etc. The habitat of Edestus would therefore seem to have been 

 somewhat similar to that of Rhizodus and Megalichtliys, of which 

 the teeth, scales, etc., are so common in the coal-shales and can- 

 nels of England and Scotland. 



In the Geological Magazine, Vol. XXIII, (1886), p. 2, Prof. 

 Henry Woodward describes and figures a fossil from the Carbon- 

 iferous rocks of Australia, to which he ffives the name of Edes- 



* That is, if the fishes which bore the spines of Edestus were carnivor- 

 ous. This is not certain, though highly probable. Vegetable eating 

 sharks, of which there may have been some in ancient times, would need 

 defensive spines even more thin those which, like Cladodus and Hybodus, 

 had teeth that were effective defensive and offensive weapons. 



