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Show 1904.] OSTEOLOGY OP THE ELOPIDJS AND ALBULIDyE. 45 portion of the opisthotic is wanting in Elops, in which genus the ventro-posterior border of the subtemporal fossa is formed by the opisthotic, and not by the exoccipital. On opening the opisthotic bulla of Megalops there is presented a fairly large cavity bounded above by the pro-otic and exoccipital, posteriorly by the exoccipital and basioccipital, anteriorly by the pro-otic, internally by the pro-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 am unable to offer any definite statement. In the recent Megalops, as in fact in the great majority, if not the whole, of the Malacopterygian fishes, the right and left pro-otic bones unite above the eye-muscle canal, and thus separate the basisphenoid from the basioccipital. I should be disposed, therefore, to regard as pro-otic that bone which in Megalops priscus touches the front of the basioccipital and is marked " 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. Temporal Series.-The supratemporal is, as in Elops, a large thin scale with a notched posterior border, projecting from the back of the cranial roof. That section of the sensory canal which normally runs antero-posteriorly in the post-temporal and supratemporal fails in Megalops to leave any impression on either of these bones, and may possibly be absent. The twTo supratemporals meet on the dorsum of the head. The post-temporal has an epiotic limb and an opisthotic limb, the latter being flattened, and not rod-like; the third limb is practically obsolete. Gircumorbital 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 anterior margin of the preorbital bone enters into a more or 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-fig. 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 minute 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 bones of large size. Mandibular Series (text-figs. 13 & 14, p. 46). -Except that it is much higher in proportion to its length, the mandible of Megalops resembles that of Elops. Hyopalatine Series (text-fig. 14, p. 46). -The hyomandibular articulates with the cranium by a single moderately broad head. The palatine has a single head for articulation with the ethmoid region. The symplectic is longer and more slender than in Elops, but the lower part of the hyomandibular is broader, and its |