218 PALEOZOIC FISHES OF NORTH AMERICA. 
cusses its relations and gives a bad figure of it. Professor Owen decided 
that it was not a jaw, but a defensive spine. 
In 1864 I described’ what proved subsequently to be a fragment of a 
spine similar to that exhibited at Providence by Professor Hitchcock, giving 
to it the name of Edestus minor. A figure taken from a photograph of a 
nearly complete specimen of this species was published in the report of 
the Geological Survey of Illinois, volume 4, Pl. I, Fig. 2, though wrongly 
named on the opposite page of explanations Edestus voraz. In the same 
volume, page 350, was published a description of a third species of Edestus, 
EF. Heinrichsi, 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 giganteus, and give in this memoir a description and a plate of it 
The geographical distribution of these species of Edestus is some,. nat 
peculiar. The first specimen described (Z. vorax) was obtained from the 
Coal Measures of Arkansas; the second (#. minor) from Park County, Ind.; 
the third (Z. Heinrichsi) from shale over coal -at Belleville, Ill., and the 
specimens of which a description and a 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. Heinrichsi from Vermillion County, Ind., and Carlin- 
ville, Ill., and of E. minor from Posey County, Ind. 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 fossils have been made, 
but not a trace of Hdestus has been found there. Hence we must infer that 
it never passed the highlands of the Cincinnati arch, which separated the 
western from the eastern coal basins. 
The material in which the spines of Hdestus are found is almost without 
exception the bituminous shale which occurs so often interstratified with the 
other elements of the Coal Measures, and very frequently resting upon coal. 
From the black shale which forms the roof of a coal mine at Belleville, 
Ill., Mr. Alexander Butters, the superintendent of this mine, has taken hun- 
! Paleontology, 2d edition, p. 124. 2 Geol. Survey Illinois, vol. 2, p. 84. 
