﻿98 1CRTHY0D0RT7L1TES. 



face flat 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 ! ; 

 but they are also abundantly met with in beds where no such teeth 

 occur. Agassiz ~ supposed that they were the spines of Psammodus ; 

 some palaeontologists have suggested 3 that they may be correlated 

 with the teeth named Cladodus, though at the same time erroneously 

 identifying certain Coal-Measure fossils with these : and Dr. J. S. 

 Newberry suspects \ from a discovery in the Waverly 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. 



Ctenacanthus major, 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, Paheontogr. vol. iii. 



p. 53, pi. viii. fig. 18 (misprint). 

 1878. Ctenacanthus tenuistriatus, L. G. de Koninck, Faune Calc. Carb. 



Belg. pt. i. p. 67, pi. vii. fig. 2. 

 (?) 1878. Ctenacanthus maximus, L. G. de Koninck, ibid. p. 68, pi. vii. 



fig. 1. [Brussels Museum.] 

 1883. Ctenacanthus major, J. W. Davis, Trans. Roy. Dublin Soc. [2] 



vol. i. p. 334, pi. xlii. figs. 1, 2. 

 1883. Ctenacanthus tenuistriatus, J. W. Davis, ibid. p. 335, pi. xliii. 



figs. 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 Log. Lower Carboniferous Limestone : Gloucestershire 

 and Belgium. Carboniferous Limestone : Shropshire. Lower Car- 

 boniferous (Posidonomyen-Schiefer) : Upper Harz 5 . 



1 See Sjphenacanthits, Pt. I. p. 241. - Poiss. Foss. vol. iii. p. 171. 



3 Hancock & Atthey, Ann. Mag. Mat. Hist. [4] vol. ix. (1872), p. 260 ; 

 J. Thomson, Trans, Glasgow Geol. Soc. -vol. iv. (1871), p. 59. 



* Eep. 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, Nouv. Mem. Soc. Imp. Nat. Moscou, vol. xiii. p. 273, pi. xxvii. fig. 18. 



