244 
SELACHIl. 
P. 2223. Four similar specimens; Dalkeith. Egerton Coll. 
P. 3117-20, P. 3122. Five similar specimens; Dalkeith. 
Enniskillen Coll. 
P. 3232. Imperfect small spine, the ornamental ridges not nodose; 
Lowmoor, Yorkshire. Enniskillen Coll. 
P. 241. Fragment of small spine; Deep Mine, Longton, Stafford¬ 
shire. Weaver-Jones Coll. 
P. 5572. Yearly complete small spine; Tibshelf Colliery, near 
Alfreton, Derbyshire. 
Presented by Edward Wilson, Esq., 1888. 
Two fragmentary spines from the /S^Vorfo's-Limestone (U. Coal- 
Measures) of Ardwick, Manchester (41251 a. Purchased , 1869), are 
also referable to Sphenacanthus; and the following species have been 
founded upon detached spines, of which there are no examples in 
the Collection:— 
Sphencicanthus cequistriatus: Ctenacanthus cequistricitus , J. W. 
Davis, Quart. Journ. Geol. Soc. vol. xxxv. (1879), p. 185, 
pi. x. fig, 15.—Lower Coal-Measures; Yorkshire. 
Sphenaccinthus minor: Ctenacanthus minor, J. M. Davis, Geol. 
Mag. [2] vol. vi. (1879), p. 531.—Lower Coal-Measures 
(Black-bed Coal); near Bradford, Yorkshire. 
Another ribbed spine from the Carboniferous of Fermanagh, 
Iieland, evidently of a similar type, is named Tristychius minor, 
J. E. Portlock, Eep. Geol. Londonderry (1843), p. 464, pi. xiv. 
fig. 6 ; and a fragmentary fossil, from the Coal-Measures of South 
Males, is referred to “ Byssacanthus ? ” by J. W. Salter, Iron-Ores 
Gt. Britain, pt. iii. (Mem. Geol. Suit., 1861), p. 224, pi. i. fig. 21. 
The fragmentary tooth from the Lower Carboniferous of Bussia, 
named Hyboclus irregularis , H. Bomanowsky (Bull. Soc. Imp. Nat. 
Moscou, 1864, pt. ii. p. 166, pi. iy. fig. 32), may belong either 
to Sphenacanihus or to Claclodus. 
Genus TRISTYCHIUS, Agassiz. 
[Boiss. 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 Hyboclus. Dorsal fin-spines with a few sharp 
longitudinal ridges distally, three only—one upon the front margin 
