EUGNATHID.E. 
325 
and ectopterygoid teeth smaller, very long and slender, and forming 
a dense cluster throughout the length of these elements ; sub¬ 
operculum of moderate size, about half as large as the nearly 
rectangular operculum. Ossifications in the sheath of the noto¬ 
chord in the form of distinct hypocentra and pleurocentra. Fulcra 
present on all the fins; distal articulations of fin-rays very close. 
Pectoral much exceeding the pelvic fins in size, but the latter large ; 
dorsal and anal fins triangular in shape, the former opposite the 
pelvic fins, the latter immediately behind it; caudal fin forked. 
Scales thin, moderately overlapping, and with a large peg-and- 
socket articulation; their exposed face ornamented with tubercula- 
tions and striae ; principal flank-scales about as deep as broad, 
several on the ventral aspect much broader than deep. Lateral 
lines inconspicuous. 
Osteorachis macrocephalus, Egerton. 
(?) 1839-44. Pachy cor mus ? macrurus, L. Agassiz, Poiss. Foss. vol. ii. 
pt. ii. p. 113, pi. Ivin, a, fig. 3. [Imperfect tail; Oxford Museum.] 
1868. Osteorachis macrocephalus, Sir P. Egerton, Quart. Journ. Geol. 
Soc. vol. xxiv. p. 500. 
1872. Osteorachis macrocephalus, Sir P. Egerton, Figs. & Descript. 
Brit. Organic Bemains, dec. xiii. (Mem. Geol. Surv.), no. 5, pi. v. 
1876. Harpcictira ( Harpactes ) velox, Sir P. Egerton, Geol. Mag. [2] 
vol. iii. pp. 441, 576. [Fish; British Museum.] 
1885. Heterolepidotus grandis, J. W. Davis, Journ. Linn. Soc., Zool. 
vol. xviii. p. 293, pi. vii. [Fish; J. W. Davis Collection, 
Halifax.] 
1890. Harpactira velox, Woodward & Sherborn, Catal. Brit. Foss. 
Vertebrata, p. 92. 
1890. Osteorhachis macrocephala, Woodward & Sherborn, ibid. p. 136. 
1890. Platysiagum grandis , Woodward & Sherborn, ibid. p. 151. 
1895. Osteorachis macrocephalus, A. S. Woodward, Geol. Mag. [4] 
vol. ii. p. 204, pi. vii. fig. 10. 
Type. Imperfect head and abdominal region ; British Museum. 
The type species, attaining a length of about 1 metre. Form 
and proportions imperfectly known, but the length of the head with 
opercular apparatus probably contained about four times, and the 
maximum depth of the trunk seven times in the total length of the 
fish. Most of the external bones ornamented with a very fine and 
close granulation ; jaws smooth. Operculum considerably deeper 
than broad. The suboperculum is more than twice as broad as 
deep in specimen no. P. 3648, and the gular plate in the same 
individual is about two-thirds as broad as long. Dorsal fin with 
not less than 18 rays, arising in advance of the middle point of the 
