﻿ICHTHYODORULITES. 129 



however, is unknown. Some of these fossils were originally named 

 Oracanthus dbbreviatus, 0. fragilis, and 0. granulatus (J . S. New- 

 berry, Bull. National Institute, 1857), but only the following two 

 species have been fully defined : — 



Acanthaspis armatus, J. S. Newberry, Rep. Geol. Surv. Ohio, 

 vol. ii. pt. ii. (1875), p. 37, pi. lv. figs. 1-6 1 . — Corniferous 

 Limestone (Lower Devonian) j Ohio. [Columbia College, 

 New York.] 



Acantholepis pustidosus, J. S. Newberry, ibid. p. 38, pi. lvi. 

 figs. 1-6 1 .— Ibid. [Columbia College, New York.] 



Genus STETHACANTHUS, Newberry. 



[Palaeoz. Fishes N. America (Mon. U. S. Geol. Surv. no. xvi. 

 1889), p. 198.] 



Spines much laterally compressed, " broadly falcate in outline, the 

 conical summit compressed, with anterior and posterior margins 

 rounded"; base of insertion broad. Convex margin with long 

 sulcus exposing the internal cavity ; concave margin at about one- 

 third of its length from the base " rising into a strong, often tumid, 

 shoulder"; sides unornamented, exhibiting the fibrous texture of 

 the spine. 



This genus is not represented in the Collection, but the two 

 following species are recognized : — 



Stethacanthus altonensis, J. S. Newberry, Palaeoz. Pishes N. 

 America (1889), p. 198, pi. xxiv. : Physonemus altonensis, 

 St. John & Worthen, Pal. Illinois, vol. vi. (1875), p. 454, 

 pi. xix. figs. 1-3. — Upper St. Louis Limestone ; Illinois 

 and Iowa. [Type species.] 



Stethacanthus tumidus, J. S. Newberry, op. cit. p. 198, pi. xxv. 

 figs. 1, 2. — Berea Grit; Berea, Ohio. [Columbia College, 

 New York.] 



In texture and general aspect the spines thus described are so 

 similar to those found with Gyracanthus, that it seems not impro- 

 bable they may truly belong to an Elasmobranch already known by 

 its fin-spines, which have received a distinct name. 



1 Both these descriptions and figures are reprinted in J. S. Newberry, 

 Palasoz. Fishes N. America (Mon. U.S. Geol. Surv. no. xvi. 1889), pp. 33-37, 

 pi. xxxi. 



PAET II. K 



