6 
CHIM^lEIDiB. 59 
P. 2846-7. One of the type specimens of Leptacanthus semistriatus , 
Agassiz, figured in the Poiss. Foss. vol. iii. pi. vii. fig. 6 ; 
also two larger portions of similar spines. 
Enniskillen Coll. 
47975-77. Portions of three similar spines. 
Presented by the Hon. Robert Mar sham, 1877. 
P. 251. Abraded spine of the same “ species.” 
Presented by J. Wood-Mason, Esq. 1880. 
P. 2213. Two nearly complete similar spines. Egerton Coll. 
P. 4173. Impression of a similar spine labelled by Agassiz thus 
“ Peut-etre le rayon du Psammodus magnus ; decrit sous 
le nom de Leptacanthus semistriatus .” Enniskillen Coll. 
P. 3108. Type specimen of Leptacanthus serratus, Agassiz, described 
and figured in the Poiss. Foss. vol. iii. (1837), p. 29, 
pi. vii. fig. 1. Enniskillen Coll. 
28596. Portion of distal half of a similar spine; Eyeford, near 
Naunton, Gloucestershire. Purchased, 1853. 
P. 6222. Crushed portion of a similar spine. 
Genus ISCH1T0DXJS ? Egerton. 
[Proc. Geol. Soc. vol. iv. 1843, p. 155.] 
Syn. Leptacanthus, L. Agassiz, Poiss, Foss. vol. iii. 1837, p. 27 (in part). 
Auluxacanthus, H. E. Sauvage, Catal. Poiss. Form. Second. Bou- 
lonnais (Mem. Soc. Acad. Boulogne, vol. ii.), 1867, p. 63. 
Ciiimceracanthus, F. A. Quenstedt, Der Jura, 1858, p. 347. 
Mandibular tooth more or less massive, with a well-defined hard 
layer upon the outer aspect immediately below the oral margin ; one 
anterior tritor usually present, sometimes several; one median 
tritor, and two or more external tritors. Palatine tooth very robust, 
with a well-defined hard layer upon the outer aspect immediately 
above the oral margin ; four tritors present, two being inner, one 
median, and one outer. Vomerine tooth more or less quadrate in 
side view, with tritors upon the oral margin; post-oral region not 
laterally expanded, and usually with a definite hard thickening. 
Dorsal fin-spine laterally compressed, smooth or longitudinally 
striated, with a double series of posterior denticles. Head-spine of 
male short, arched, with a terminal cluster of denticles. 
