24 
actinoptertgii. 
Genus MEGALOPS, Lacepedo. 
[Hist. Nat. Poiss. vol. v. 1803, p. 289.] 
Head and trunk laterally compressed, but abdomen flattens I 
Parietal bones in contact in the median line; mandible a l^® j 
prominent ; two supramaxillary bones ; eye relatively very larg e » 
margin of the jaws, the vomer, parasphenoid, palatine, and 
gold bones, and the tongue, with clusters of minute pointed tee 
ill-i akers long and slender; operculum subdivided by transverse j 
suture, branchiostegal rays about 25 in number. Pectoral a 11 j 
pelvic fins each with an enlarged and elongated scale at the base- 1 
orsal fin short-based and elevated, with much-produced hindenn° s j 
ray, opposite or immediately behind pelvic pair; anal fin iu ° r _ I 
extended than the dorsal, but also with produced hindermost ray! 
caudal fin deeply cleft. Scales not ornamented ; sensory canal 
lateral line radiating on the scales it traverses. j 
The skull of the existing Megalops is described and figured J 
H. W. Shufeldt, Ann. Hep. U.S. Commiss. Fisheries, 1883 (1885), j 
p. 814, pi. xiv. figs. 33, 34. 
Megalops prisons, sp. nov. 
[Plate III. figs. 3-6.] 
1844-45. Megalops prigeus, L. Agassiz, Poiss. Foss. vol. v. pt. «■ P- 114 
_ ( name only), and Rep. Brit. Assoc. 1844, p. 308 (name only)- 
1844. Hypsodon toHapicus, L. Agassiz, ibid. vol. v. pt. i. p. 101 l nalU 
only). 
1854 Megalops priscus, R. Owen, Catal. Foss. Rept. & Pisces, M" 9 - 
oy. Coll. Surg. p. 172 (no description). 
Type. Imperfect head ; British Museum. 
An imperfectly known large species, the head with opcrcula* 
apparatus attaining a length of at least 0-3. Length of head nearl) 
equalling its depth behind, and about twice as great as the maxi® 11 ® 
wi th of the operculum ; length of cranial roof from occiput to p 08 
trontal considerably less than its width at the position of the latte* 
e ement. Maxilla extending backwards beyond the orbit ; opercu a* 
ones and cnees-piates radiately sculptured. 
Form. S( Loc. Lower Eocene (London Clay) : Sheppey. 
36070. Head with opercular apparatus, to be regarded as the t)p e 
specimen, shown of ono third the natural size from t 
left lateral and superior aspects in PI. III. figs- * 7 *' 
The cranium is very imperfectly preserved, and t 
sutures between its elements arc not distinct; hut t 
contour of its roof is shown (fig. 3 a), gradually \videm n S 
