98 
ICHTHYODORTJLITES. 
face fiat or concave, with a series of small denticles upon each 
margin. 
Spines of this character doubtless characterize more than one 
genus. They have already been discovered in association with 
hybodont teeth, indicating a shark with two armed dorsal fins 1 ; 
but they are also abundantly met with in beds where no such teeth 
occur. Agassiz 2 supposed that they were the spines of Psammodus ; 
some palaeontologists have suggested 3 that they may be correlated 
with the teeth named Clcidodus , though at the same time erroneously 
identifying certain Coal-Measure fossils with these ; and Dr. J. S. 
Newberry suspectsfrom a discovery in the AVaverly Shales of Ohio, 
that Ctenacanthus and Orodus may be synonymous. It is certainly 
noteworthy that in Britain the largest spines of this type occur in 
the Bristol Carboniferous Limestone, where also are discovered the 
largest teeth of Orodus : and the “ species ” are most numerous at 
Armagh, where Orodus exhibits the greatest variety. 
Ctenacaiatlius maj©r 9 Agassiz. 
1837. Ctenacanthus major , L. Agassiz, Poiss. Foss. vol. iii. p. 10, pi. iv. 
1837. Ctenacanthus tenuistriatus , L. Agassiz, ibid. p. 11, pi. iii. figs. 
7-11. [Bristol Museum and British Museum.] 
1850. Ctenacanthus tenuirostris, F. A. Roerner, Pakeontogr. vol. iii. 
p. 53, pi. viii. fig. 18 (misprint). 
1878. Ctenacanthus tenuistriatus, L. G. de Koninck, Faune Calc. Garb. 
Belg. pt. i. p. 67, pi. vii. fig. 2. 
(P) 1878. Ctenacanthus maximus, L. G. de Koninck, ibid. p. 68, pi. vii. 
fig. 1. [Brussels Museum.] 
1883. Ctenacanthus major, J. W. Davis, Trans. Boy. Dublin Soc. [2] 
vol. i. p. 334, pi. xlii. figs. 1, 2. 
1883. Ctenacanthus tenuistriatus, J. W. Davis, ibid. p. 335, pi. xliii. 
hgs- 1, 2. 
1883. Ctenacanthus salopiensis, J. W. Davis, ibid. p. 339, pi. xliv. fig. 6. 
[British Museum.] 
Type. Bristol Museum. 
The type species, attaining a very large size. 
Form. Sf Loc. Lower Carboniferous Limestone: Gloucestershire 
and Belgium. Carboniferous Limestone : Shropshire. Lower Car¬ 
boniferous (Posidonomyen-Sckiefer) : Dpper Harz 3 . 
1 See Sphenacanthus, Pt. I. p. 241. ~ Poiss. Foss. vol. iii. p. 171. 
3 Hancock & Atthey, Ann. Mag. ISat. Hist. [4] vol. ix. (1872), p. 260 ; 
J. Thomson, Trans, Glasgow Geol. Soc. vol. iv. (1871), p. 59. 
4 Rep. Geol. Survey Ohio, vol. ii. pt. ii. (1875), p. 54. 
5 A fragmentary spine, of doubtful species, from the Lower Carboniferous 
Limestone of the Govt, of Toula, is also named Ctenacanthus major , H. Traut- 
schold, Kouv. Mem. Soc. Imp. hat. Mosoou, vol. xiii. p. 273, pi. xxvii. fig. 18. 
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