MYRIACAXTHII).®. 
51 
punctate dentine appears to be exposed only in a long 
narrow band on each of these two elevations. 
Enniskillen Coll. 
P. 3070. Imperfectly preserved distal portion of dorsal spine, the 
type specimen of Myriacanthus grcimdatus. 
Enniskillen Coll. 
P. 2848. Much broken distal extremity of dorsal spine in hard 
matrix, the type specimen of Leptacanthus tenuispinus. 
Enniskillen Coll. 
43065. Much abraded dorsal spine, wanting the basal portion. 
Purchased , 1871. 
P. 3072, P. 4454 b-e. Two imperfectly preserved dorsal spines, 
wanting the basal portion; also three fragments. 
Enniskillen Coll. 
P. 4876. Crushed spine, wanting anterior denticles. 
Purchased , 1885. 
41382. Distal portion of spine. Purchased , 1869. 
The following specimen is also probably referable to Myria¬ 
canthus :— 
P. 2850. Distal portion of dorsal spine, exhibiting a nearly smooth, 
slender, arcuated extremity, with four widely-spaced, large 
and downwardly curved posterior denticles, shown, of the 
natural size, in PI. III. fig. 5 ; Lower Lias, Lyme Regis. 
Enniskillen Coll. 
Genus OHIM^IROPSIS, Zittel. 
[Handb. Palaeont. vol. iii. 1887, p. 113.] 
Mandibular tooth with an undulating or gently curved oral 
surface and margin, with an extended, punctate, tritoral area. 
Presymphysial tooth vertically elongated, bilaterally sjmmetrical; 
the inner aspect flat or concave, the outer aspect convex. Palatine 
tooth thin, plate-like, triangular, and pointed behind. Vomerine 
tooth somewhat larger than the palatine, triangular, and pointed 
anteriorly; oral surface with an anterior and a posterior punctate 
tritoral area. Dorsal fin-spine elongated, more or less laterally 
compressed, and the sides ornamented with tuberculations; a series 
of large, thorn-shaped, spinous tubercles arranged along each side 
of the flattened posterior face, and a single series of similar denticles 
occupying at least part of the anterior border. Dermal plates 
tuberculated ; trunk covered with small, conical, radiately grooved 
granules. {Zittel.) 
e 2 
