﻿ICHTHTODORULITES. 



139 



The following species of Oracanthus have also been described, 

 but, in some cases, the distinctive features are very slight, and if 

 such were regarded as of specific value in Britain, 0. milleri would 

 be considerably subdivided : — 



Oracanthus armigerus, E,. H. Traquair, Trans. Edinb. Geol. Soc. 

 vol. v. (1887), p. 313 (name only), and Geol. Mag. [3] 

 vol. v. (1888), p. 86. — Calciferous Sandstones; Abden, 

 Fife, and Eskdale, Dumfries. Carboniferous Limestone ; 

 Ayrshire. [Collection of R. Craig, Esq., and also portion 

 of fish in Edinburgh Museum.] 



Oracanthus? obliquus, St. John & Worthen, Pal. Illinois, vol. vi. 

 (1875), p. 477, pi. xxii. fig. 16.— Upper Keokuk Lime- 

 stone ; Illinois. 



Oracanthus rectus, St. John & Worthen, op. cit. vol. vii. (1883), 

 p. 257, pi. xxv. fig. 3. — Chester Limestone ; Illinois. 



Oracanthus trigonalis ; Pnigeacanthus trigonalis, St. John & 

 Worthen, op. cit. vol. vii. p. 259, pi. xxiv. fig. 4. — St. 

 Louis Limestone ; Illinois. 



Oracanthus vetustus, J. Leidy, Proc. Acad. Nat. Sci. Philad. vol. vii. 

 1856, p. 414, and Journ. Acad. Nat. Sci. Philad. [2] 

 vol. iii. (1856), p. 161, pi. xvi. figs. 1-3 ; St. John & 

 "Worthen, op. cit. vol. vii. p. 255, pi. xxiv. fig. 2 : Ora- 

 canthus consimilis, St. John & Worthen, op. cit. vol. vi. 

 p. 478, pi. xxii. fig. 15. — Upper St. Louis Limestone; 

 Illinois, Missouri, and Iowa. [Academy of Natural Sci- 

 ences, Philadelphia.] 



Closely related to Oracanthus is the very large spine described as 

 follows: — 



Antacanthus insignis, G. Dewalque, Ann. Soc. Geol. Belg. vol. v. 

 (1877), p. lx; L. G. de Koninck, Paune Calc. Carb. Belg. 

 pt. i. pp. 72, 73, pi. viii. figs. 1-3. — Lower Carboniferous 

 Limestone ; Liege. [University of Liege.] 



Genus GYRACANTHUS, 



[Poiss. Eoss. vol. iii. 1837, p. 17.] 



Syn. Mitrodus, R Owen, Trans. Odontol. Soc. vol. v. 1867, p. 338. 



Spines of two distinct types, the one evidently connected with 

 fins, the other free. Fin-spines elongated, robust, more or less 

 arched, irregularly rounded or oval in transverse section, except 

 towards the unworn apex, which is compressed ; base of insertion 

 large, with the internal cavity open for a considerable extent pos- 



