24 
ACTINOPTEEYGII. 
Genus MEGALOPS, LacepMe. 
[Hist. Hat. Poiss. vol. v. 1803, p. 289.] 
Head and trunk laterally compressed, but abdomen flattened. 
Parietal bones in contact in the median line; mandible a little 
prominent; two supramaxillary bones; eye relatively very large ; 
margin of the jaws, the vomer, parasphenoid, palatine, and ptery¬ 
goid bones, and the tongue, with clusters of minute pointed teeth. 
Gill-rakers long and slender; operculum subdivided by transverse 
suture; branchiostegal rays about 25 in number. Pectoral and 
pelvic flns each with an enlarged and elongated scale at the base; 
dorsal fln short-based and elevated, with much-produced hindermost 
ray, o^Dposite or immediately behind pelvic pair; anal fin more 
extended than the dorsal, but also with produced hindermost ray; 
caudal fin deeply cleft. Scales not ornamented ; sensory canal of 
lateral line radiating on the scales it traverses. 
The skull of the existing Megalops is described and figured by 
R. W. Shufeldt, Ann. Eep. U.S. Commiss. Fisheries, 1883 (1885), 
p. 814, pi. xiv. figs. 33, 34. 
Megalops priscus, sp. nov. 
[Plate III. figs. 3-6.] 
1844-45. Megalops priscus, L, Agassiz, Poiss. Foss. vol. v. pt. ii. p. 114 
(name only), and Hep. Brit. Assoc. 1844, p. 308 (name only). 
1844. Hypsodon toliapicus, L. Agassiz, ibid, vol, v, pt. i. p. 101 (name 
only). 
1854. Megalops priscus, R. Owen, Catal. Foss. Rept. & Pisces, Mus, 
Roy. Coll. Surg. p. 172 (no description). 
Type. Imperfect head; British Museum. 
An imperfectly known large species, the head with opercular 
apparatus attaining a length of at least 0-3. Length of head nearly 
equalling its depth behind, and about twice as great as the maximum 
width of the operculum ; length of cranial roof from occiput to post¬ 
frontal considerably less than its width at the position of the latter 
element. Maxilla extending backwards beyond the orbit; opercular 
bones and cneeK-piates radiately sculptured. 
Form. ^ Log. Lower Eocene (London Clay); Sheppey. 
36070. Head with opercular apparatus, to be regarded as the type 
specimen, shown of one third the natural size from the 
left lateral and superior aspects in PL III. figs. 3, 3 a. 
The cranium is very imperfectly preserved, and the 
sutures between its elements are not distinct; but the 
contour of its roof is shown (fig. 3 a), gradually widening 
