1904.] OSTEOLOGY OF THE ELUPID.E AND ALBULID.E. 45 



portion of the opisthotic is wanting in Ulops, in which genus the 

 ventro-posterioi- border of the subtempoi'al fossa is formed by the 

 opisthotic, and not by the exoccipital. 



On opening the opisthotic bulla of Megcdops there is presented 

 a faii'ly large cavity bounded above by the pro-otic and exoccipital, 

 posteriorly by the exoccipital and basioccipital, anteriorly by the 

 pro-otic, internally by the pi'O-otic, exoccipital, and basioccipital, 

 ventrally and externally by the opisthotic. The chamber opens 

 postero-ventrally at the side of the basioccipital, and probably 

 contains a diverticulum of the swim-bladder ; but on this point I 

 a,m una,ble to oifer any definite statement. 



In the recent Megalops, as in fact iir the great majority, if not 

 the whole, of the Malacopterygian fishes, the right and left pro- 

 otic bones unite above the eye-mviscle canal, and thus separate 

 the basisphenoid from the basioccipital. I should be disposed, 

 therefore, to regard as pro-otic that bone which in Megcdops priscits 

 touches the fi-ont of the basioccipital and is marke<l '' basisphenoid " 

 by Smith Woodward (Brit. Mus. Cat. Foss, Fish. iv. pi. iii. fig. 5 ; 

 also p. 26, specimens P. 356 and P. 1698). 



The basisphenoid is rather slender, and is T-shaped when seen 

 from the front. The body of it lies between the two pro-otics and 

 does not touch the alisphenoids. The orbitosphenoid is similar 

 to that of Elops. 



Teviporcd Series. — The supiuteiaporal is, as in Elops, a lai-ge 

 thin scale with a notched posterioi- boi'der, pi-ojecting from the 

 back of the cranial roof. That section of the sensory canal which 

 normally runs antero-posterioi-ly in the post-temporal and supia- 

 tempoi'al fails in Megcdops to leave any impression on either of 

 these bones, and may possibly be absent. The two supi'atempoi'als 

 meet on the dorsum of the head. The post-tempoiul has an 

 epiotic limb and an opisthotic limb, the latter being flattened, 

 and not rod-like ; the third limb is practically obsolete. 



Oii-cumorhltcd Series (text-fig. 13, p. 46). — This series consists 

 of a nasal bone and nine bones around the eye ; the orbital ring- 

 is incomplete above. The anterioi- margin of the preorbital bone 

 enters into a more oi- less definite articulation with the back of 

 that head of the maxilla which engages with the palatine. The 

 corresponding articulation in Elops is of a less definite character. 



Maxillary Series (text-Q-g^. 13, p. 46). — The gape is large, but not 

 so large as in Elops ; it is bounded above by the premaxilla and 

 maxilla. The teeth are miniite and densely set on the edges of 

 both of these bones, and extend nearly to the posterior end of 

 the maxilla. There are two surmaxillary liones of lai-ge size. 



Mandihidar Series (text-figs. 13 & 14, p. 46). — Except that it is 

 much higher in proportion to its length, the mandible of Megcdops 

 resembles that of Elops. 



Hyopcdatine Series (text-fig. 14, p. 46). — The hyomandibular 

 articulates with the cranium by a single moderately broad head. 

 The palatine has a single head foi' articulation with the ethmoid 

 region. The symplectic is longer and more slender than in Elops, 

 but the lower part of the hyomandibular is broadei-, and its 



