FISHES OF THE CARBONIFEROUS SYSTEM. 225 
EDESTUS GIGANTEUS, 0. Sp. 
Plate XLI, Fig. 1. 
Spine very large, eighteen inches or more in length by seven and a 
half inches in breadth to top of denticles, and two inches in thickness at 
center; form strongly arched, section spatulate in the middle, lenticular at 
base; lateral surfaces of bony portion vermicularly roughened; segments 
narrow, running far back, about three-quarters of an inch wide, in the mid- 
dle of the spine ten inches from summit of denticle to lower margin; den- 
ticles three and a half inches long by two and a quarter inches wide at base; 
triangular in outline, crown about as broad as high, base prolonged back- 
ward and downward into a simple curved point; margins set with fifteen to 
eighteen strong, rounded, compressed crenulations. 
This remarkable spine differs from the other species of the genus not 
only by its greater size but by the form of its enameled denticles. It ap- 
proaches nearest to Edestus vorax,' Leidy, but is distinguished from that 
species by its larger size, more prolonged segments, and especially by the 
outline of the bases of the denticles. In LZ. vorax the enameled surface of 
the denticles is nearly horizontal and is rounded behind, with a deep 
notch. In the species before us, on the contrary, the enamel runs down 
obliquely backward to an acute point, from which it sweeps upward by 
a gentle curve, forming a shallow sinus, to the base of the posterior row of 
serrations. 
From Edestus Heinrichsi,? N. & W., it differs by its greater size, more 
curved form, more oblique denticles, and the shorter posterior point of the 
base. 
From Edestus minor,® Newb. (wrongly named Edestus vorax on the 
page of explanations, opposite the plate in Geology of Illinois, volume 4), it 
differs in its much greater size and the far broader and less decurrent den- 
ticles, as will be seen from the figures now given, reproduced from photo- 
graphs of the two last-mentioned species. 
! Described in Proc. Acad. Nat. Sci. Phila., vol. 7, p. 414, and in the Journal of the same Academy, 
2d series, vol. 3, 1856 (1858), p. 159, pl. 15. 
2Geol. Illinois, vol. 4, p. 350, pl. 4, fig. 1. 
3Tbid., vol. 2, p. 84, pl. 4, fig. 24; vol. 4, pl. 1, fig. 2. 
MON XVI 15 
