M YBIACANTHID2E. 
49 
Myriacanthus granulatus, Agassiz. 
[Plate II. fig. 4; Plate III. figs. 3, 4.] 
1837. Myriacanthus yranulatus, L. Agassiz, Poiss. Foss. vol. iii. p. 40, 
pi. viii. a. fig. 16. 
1837. Leptacanthus tenuispinus, L. Agassiz, ibid. p. 27, pi. i. figs. 12,13. 
[Spine; British Museum.] 
1871. Ischyodus orthorhinus, Sir P. Egerton, Quart. Journ. Geol. Soc. 
vol. xxvii. p. 27o, pi. xiii. [Head, &c.; British Museum.] 
1887. Metopcicanthus orthorhinus, K. A. von Zittel, Handb. Palseont. 
vol. iii. p. 111. 
1889. Myriacanthus yranulatus, A. S. Woodward, Ann. Mag. Nat. 
Hist. [6] yoI. iv. p. 279. 
Type. Imperfect dorsal fin-spine : British Museum. 
A species of comparatively small size, the dorsal spine attaining 
a maximum length of about 0*18. Dorsal spine much laterally 
compressed, with an acute anterior edge ; lateral tubercles relatively 
small and closely arranged, absent upon a long extent from the 
much attenuated apex; anterior and posterior denticles long, com¬ 
paratively slender, and closely arranged : a long series of the pos¬ 
terior denticles distally directed downwards, the others pointing 
upwards. Maximum thickness of presymphysial tooth about one 
third its breadth, and the tritor confined to a narrow median 
band, lenticular in section ; outer face of the tooth strongly convex, 
with a sharply rounded, median, longitudinal elevation, the inner 
face equally concave. 
This is the type species of the so-called Metopcicanthus. 
Form. 6f Loc. Lower Lias : Lyme Begis, Dorsetshire. 
43050. Head and associated dorsal fin-spine in position, described 
and figured by Egerton, loc. cit., as the type specimen of 
Ischyoclus orthorhinus, and subsequently adopted as the 
type of Metopcicanthus by Zittel, loc. cit. The rostral spine 
is shown to be covered superiorly with granulations, finer 
and more closely arranged than those of the sides of the 
dorsal spine. Purchased , 1871. 
P. 4575. Bemains of the head with dentition, and the basal half of 
the rostral spine; also a fragment of the dorsal spine, 
probably found associated. The jaws and a few dermal 
tubercles are shown, of the natural size, in PI. II. fig. 4, 
and the parts are indicated by the lettering. A portion of 
the cartilage of the mandible is seen from the outer ante¬ 
rior aspect; and overlapping the oral margin is observed 
the pair of large mandibular teeth (pul.). Immediately 
Ii 
PAST II. 
