from the Carboniferous of Western Australia. 3 



of the jaw is its segmented character ; and of the segments the 

 fossil retains two very nearly perfect ones with portions of two 

 others. Each segment in outline forms an irregular pentahedron ; 

 and each possesses a single coossified tooth, whose broad surfaces 

 abruptly increase the acclivity of the sides of the jaw." 



This specimen is most probably from the Carboniferous series, 

 and was found at Frozen Rock, Arkansas River, 20 miles below 

 Fort Gibson, in the Indian Territory. 



Prof. J. S. Newberry describes a much smaller specimen, under 

 the name of Edestus minor, in the Geol. Surv. of Illinois, vol. ii. 1866, 

 p. 84, and gives a figure on plate iv. fig. 24. This figure repre- 

 sents one tooth only, 10 lines long, and 5^ lines wide at base, and 

 3 lines thick, set saddle-like upon the edge of a flat, bony jaw. This 

 specimen was obtained from the Coal Measures, Posey County, 

 Indiana. In vol. iv. of the same work, at p. 350, Newberry and 

 Worthen describe and figure, pi. i. fig. la, 16, another specimen 

 under the name of Edestus Heinrichsii, from the Coal Measures of 

 Belleville, Illinois. The following is the description given by 

 Messrs. Newberry and Worthen of Edestus Heinrichsii, N. & W., 

 1870 : ' — " Spine robust, one foot or more in length, by two and a half 



Fig. 1.— Part of the spine of Edestus ip-f" (E. Seinriehsii?), Coal M., Indiana. 



inches wide, and one and a quarter inch thick, composed of dense, 

 bony tissue, symmetrically flattened, with an ovoid section below ; 

 lenticular above ; one margin nearly straight, the other gently 

 arched ; the basal end irregularly rounded off; the arched border 

 set with nine large, triangular, flattened, doubly crenulated, 

 enamelled denticles, each about an inch in height, the upper 

 half of the straight line forming a sharp cutting edge. The 

 denticles of the arched border are broadly triangular in outline, 

 rising perpendicularly from the curved edge on which they 

 rest, each three-quarters of an inch in height, by one and a quarter 

 inch in breadth, compressed laterally, with crenulated cutting edges. 

 They are contiguously placed, and each is embraced by the acute 



1 Geological Survey of Illinois, vol. iv. Geology and Palaeontology, 4to, Illinois, 

 1870, pp. 350-353, pi. i. figs, la and lb. Some confusion exists in the references to the 

 figures here ; for of the two species drawn on the plate, the one named E. Heinrichsii 

 agrees best with Leidy's original figure ; whilst the one named E. vorax, which agrees 

 with our woodcut {supra), has much larger denticles. 



