476 
ACTINOPTERYGII. 
The following specimens are not specifically determined : — 
P. 5205. Fragment of left dentary, rather stout and large, showing 
bases of teeth ; London Clay, Sheppey. / Gardner Coll. 
25740. Anterior end of small right dentary; Middle Eocene, 
Bracklesham Bay. Dixon Coll. 
The indefinable Scombroid genus Stereodus (B. Owen, Geol. Mag. 
vol. ii. 1865, p. 147), from the Miocene of Malta, has smooth, 
round teeth much like those of Scomhramphodon. The large type 
species, Stereodus melitensis (R. Owen, loc. cit., and J. H. Cooke, 
Geol. Mag. [3] vol^ viii. 1891, p. 546), is represented in the Col¬ 
lection by the following specimens, ail from the yellow limestone of 
Malta and Gozo:— 
P. 3903. Imperfect base of caudal fin. Enniskillen Coll. 
P. 6207. Terminal caudal vertebrae and remains of caudal fin-rays. 
Each vertebra in advance of the hypural exhibits two 
lateral pits separated by a rounded median longitudinal 
ridge. Presented hy Sir John Murray, K.C.B., 1890. 
P. 6207 a. Nearly similar specimen, but having two very short and 
deep vertebral centra, without median lateral ridge, im¬ 
mediately in front of hypural. 
Presented hy Sir John Murray, K.C.B., 1890. 
P. 343. Nearly similar specimen, but three last ridged caudal 
vertebral centra relatively shorter and deeper. 
Purchased, 1881. 
P. 7537. Various remains of end of tail and caudal fin-rays. 
Presented by P. T. Godsal, Esq., 1895. 
The fragment of jaw from the Middle Oligocene of Flonheim, in 
the Mayence Basin, named Sphyraenodus conoideus by H. von Meyer 
(Neues Jahrb. 1846, p. 597, and Palaeoutogr. vol. i. 1851, p. 281, 
pi. xxxiii. fig. 13), closely resembles the so-called Stereodus. 
Genus THYRSITOCEPHALUS, G. vom Rath. 
[Zeitschr. deutsch. geol. Ges. vol. xi. 1859, p. 114.] 
Trunk elongated and laterally compressed. Orbit relatively 
small; mandible prominent; teeth few and large, smallest in front 
of the jaws. Vertebrae about 54 in number, nearly half being 
abdominal; ribs small. Paired fins small; dorsal fins scarcely 
