114 Belations of Edestus. 



should continue sepai'ated, each part with teeth only on one 

 side, would not be much unlike the fossil." He suggested that 

 the fish had a corresponding jaw projecting from the opposite 

 side of its head, and that both formed a powerful weapon of of- 

 fence. He legarded it as belonging not only to an undescribed 

 genus, but to a new family of fishes. 



This specimen was obtained by the Rev. John Hawks, in Park 

 County, Indiana, "in a layer of shale overljing a coal seam." 

 Subsequently it was submitted by Dr. Hitchcock to Prof. Rich- 

 ard Owen, of London, who discusses its relations on p. 194 of 

 his Palaeontology, second edition, and gives a bad figure of it. 

 Prof. Owen decided that it was not a jaw, but a defensive spine. 



In 1866 I described in Vol. II, of the Geology of Illinois, p. 

 84, a portion of what proved subsequently to be a fragment of a 

 spine similar to that exhibited at Providence by Prof. Hitch- 

 cock, giving to it the name of Edestus minor. K figure, taken 

 from a photograph of a nearly complete specimen of this species, 

 was published in Vol. IV. of the Illinois Report, PL I, fig. 2, 

 though wrongly named on the opposite page of explanations, 

 Edesttis vfirax. In the same volume, p. 350, was })ublished a 

 description of a third species of Edestus, E. Hein7nclisii, and a 

 half-size figure is given on the plate cited above. To these three 

 species, I now add a fourth of gigantic size, which I have named 

 Edestus giganttiis. and give in this memoir a description and 

 figure of it. 



The geographical distribution of these species of Edestus is 

 somewhat peculiar. The first specimen described (E. vorax) 

 was obtained from the Coal Measures of Arkansas ; the second 

 {E. 71117101'), from Park County, Indiana ; the third {E. Hein- 

 richsii), from shale over coal at Belleville, Illinois, and the spec- 

 imen of which a description and figure are now published is 

 from the coal-shale at Decatur, in the same State. I should also 

 say that I have other specimens of E. Heinriclisii, from Vermil- 

 lion Co., Indiana. Thus it will be seen that all the specimens 

 known, now quite numerous, are from the Mississippi coal field; 

 that is, the coal area of Illinois and Missouri, once continuous, 

 but now separated by the erosion of the immediate valley of the 

 Mississippi. 



In Ohio and Pennsylvania, much more extensive excavations 

 in the coal rocks, and numerous collections of Carboniferous 



