476 
ACTINOPTERYGII, 
The following specimens are not specifically determined : — • 
P. 5205. Fragment of left dontary, rather stout and large, showing 
bases of teeth ; London Clay, Sheppey. Gardner Coll- 
25740. Anterior end of small right dentary; Middle Eocene, 
Brackleshatn Bay. Dixon Coll- 
The indefinable Scombroid genus Stereodus (R. Owen, Geol. Mag. 
v °l. i*. 1865, p. 147), from the Miocene of Malta, has smooth, 
round teeth much like those of Scombramphodon. The largo typ e 
species, Stereodus melilensis (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, all from the yellow limestone of 
Malta and Gozo : — 
P. 3903. Imperfect base of caudal fin. Enniskillen toll- 
P. 6207. Terminal caudal vertebrae and remains of caudal fin-rays. 
Each vertobra in advance of the hypural exhibits two 
lateral pits separated by a roundod median longitudinal 
ridge. Presented by Sir John Murray, K.C.B - , 1899. 
P. 6207 a. Nearly similar spocimcn, but having two very short and 
deep vertebral centra, without median lateral ridge, im- 
mediately in front of hypural. 
Presented by Sir John Murray, K.C.B-, 1896. 
P- 343. Nearly similar specimen, hut 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 Flonhcim, in 
the Mayence Basin, named Sphyrcenodus conoideus by H. von Me} cr 
(Neues Jahrb. 1846, p. 597, and I’ahnontogr. vol. i. 1851, p. -181, 
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, smallost in Iront 
of the jaws. Vertebrae about 54 in number, nearly half bein 0 
abdominal ; ribs small. Paired fins small ; dorsal fins scarcely 
