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ICHTHYOTOMI 
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Genus FLEUEAOANTHUSj Agassiz. 
[Poiss. Foss.-vol. iii. 1837, p. 66.] 
Syn. Diplodus , L. Agassiz, Poiss. Foss. vol. iii. 1843, p. 204. 
Orthacanthus, L. Agassiz, torn. cit. 1843, pi. 45. figs. 7-9. 
^ Aa O^T^yXencicant hus. E. Beyrich, Monatsb. Verb. k. Preuss. Akad. Wiss. 
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1848, p. 24. 
Triodus, Jordan, Nenes Jahrb. 1849, p. 843. 
Compsacanthus, J. S. Newberry, Proc. Acad. Nat. Sci. Pbilad. 
1856, p. 100. 
Dittodus , R. Owen, Trans. Odont. Soc. vol. v. 1867, p. 325. 
Aganodus, R. Owen, tom. cit. p. 359. 
Ochlodus, R. Owen, torn. cit. p. 346. 
Pternodus, R. Owen, tom. cit. p. 363. 
Thrinacodus , St. John & Wortken, Pal. Illinois, vol. yi. 1875, 
p. 289. 
Lophacanthus , T. Stock, Ann. Mag. Nat. Hist. [5] vol. v. 1880, 
p. 217. 
Anodontacanthus, J. W. Davis, Quart. Journ. Geol. Soc. 
vol. xxxvii. 1881, p. 427. 
Didymodus, E. D. Cope, Proc. Acad. Nat. Sci. Pbilad. 1883, 
p. 108. 
.yAP./tfA/cr /sr.a^or. f-7 <*t * 
Body probably destitute of shagreen; a long barbed spine, with 
two series of denticles, placed dors ally immediately behind the head. 
Teeth with thick depressed root, the crown consisting of two prin¬ 
cipal divergent cones, generally of unequal size, with a more or less 
minute intermediate denticle, and often a round flat-topped boss 
(“ button ”) behind. 
The generic identity of the Ashes bearing the spines named 
Pleuracanthus and Xenacanthus, and the teeth named Diplodus, was 
first pointed out by Egerton 1 . Triodus was also referred to the 
same genus by Schnur 2 , and Orthacanthus by J. W. Davis 3 . Zittel 
lias already remarked 4 upon the probable identity of Compsacanthus 
with the so-called Orthacanthus; and Traquair has determined 5 the 
identity of Anodontacanthus, in part, with the spines of the present 
genus. The name Thrinacodus was given by St. John and Worthen to 
teeth differing from those of “Diploclus” in the absence of a “ button " 3 
—a character apparently inconstant, as noted by Cope 6 . Dittodus , 
1 Ann. Mag. Nat. Hist. [2] vol. xx. (1857), p. 423. 
2 Zeitschr, deutsch. geol. Gesell. vol. viii. (1856), p. 542. 
3 Quart. .Tourn. Geol. Soc. vol. xxxvi. (1880), p. 331, 
4 Handb. Pakeont. vol. iii. pt. i. (1887), p. 90. 
5 Geol. Mag. [3] vol. v. (1888), p. 101. 
6 Proc. Amer. Phil. Soc. 1884, p. 589. 
