244 
SELACnil. 
P. 2223. Four similar specimens; Dalkeith. Egerton Coll. 
P. 3117-20, P. 3122. Five similar specimens; Dalkeith. 
EnnisTciUen Coll. 
P. 3232. Imperfect small spine, the ornamental ridges not nodose ; 
Lowmoor, Yorkshire. EnnislcUlen Coll. 
P. 241. Fragment of small spine ; Deep Mine, Longton, Stafford- 
shire. Weaver-Jones Coll. 
P. 5572. Nearly complete small spine ; Tihshelf Colliery, near 
Alfreton, Derbyshire. 
Presented hy Edward Wilson, Esq., 1888. 
Two fragmentary spines from the /S^jjVorifVLimostone (D. Coal- 
Measures) of Ardwick, Manchester (41251 a. Purchased, 1869), are 
also referable to Sjohenacanfhus ; and the following species have been 
founded upon detached spines, of which there are no examples in 
the Collection ; — 
Sj>henacanthus aquistriatus : Ctenacanilius acjuislriatus, J. W. 
Davis, Quart. Journ. Gcol. Soc. vol. xxxv. (1879), p. 185, 
pi. X. fig. 15. — Lower Coal-Measures ; Yorkshire. 
Sqdienacantlms minor: Ctenacauthns minor, J. W. Davis, Geol. 
Mag. [2] vol. vi. (1879), p. 5!51. — Lower Coal-Measures 
(Black-bed Coal) ; near Bradford, Yorkshire. 
Another ribbed spine from the Carboniferous of Fermanagh, 
Ireland, evidently of a similar type, is named Tristychius minor, 
J. E. Portlock, Bop. Geol. Londonderry (1843), p. 464, pi. xiv. 
fig. 6 ; and a fragmentary fossil, from the Coal-Measures of South 
Wales, is referred to “ Byssafanthusl ” by J. W. Salter, Iron-Ores 
Gt. Britain, pt. iii. (Mem. Gcol. Suit., 1861), p. 224, pi. i. fig. 21. 
The fragmentary tooth from the Lower Carboniferous of Russia, 
named IJybochis irregularis, H. Eomanowsky (Bull. Soc. Imp. Nat. 
Moscou, 1864, pt. ii. p. 166, jd. iv. fig. 32), may belong cither 
to Sqihenacanthus or to Cladodus. 
Genus TRISTYCHIUS, Agassiz. 
[Poiss. Foss. vol. iii. 1837, p. 21.] 
Syn. Ptychacanthus, L. Agassiz, tom. cit. 1837, p. 22. 
Teeth not certainly identified, but probably resembling those of 
Sphenacanthus and Hyhodus. Dorsal fin-spines with a few sharp 
longitudinal ridges distally, three only — one upon the front margin 
