This family, which appears to me to be related to the Dapediidae, is provisionally placed here by A. S. Woodward on account of its resemblance to the Leptolepididae, but it is not yet quite clear that the mandible was destitute of splenial and coronoid elements, while the bones at the base of the pectoral fin have not hitherto been observed. The principal genera are Pholidophorus, ranging from the Upper Trias to the Purbeck; Thoracopterus, from the Upper Trias; and Pleuropholis, from the Upper Jurassic. The species of Pholidophorus are very numerous in the Jurassic period, and Woodward has observed that the scales of the later species are more elaborately ornamented than those of earlier date.
Fam. 2. Archaeomaenidae.—Distinguished from the preceding by the thin, cycloid scales. Conspicuous obtuse ridge-scales are present along the dorsal and ventral lines. Archaeomenes, from the Jurassic (?) of New South Wales.
Fam. 3. Oligopleuridae.—Characters as in Pholidophoridae, but scales cycloid and vertebrae completely or nearly completely ossified.
Oligopleurus, from the Jurassic of England and France; Oenoscopus, from the Jurassic and Cretaceous of France, Germany, and Italy; and Spathiurus, from the Cretaceous of Mount Lebanon and Dalmatia.
Fam. 4. Leptolepididae.—Praemaxillaries very small; maxillaries large, loosely attached; teeth small and conical. Parietal bones separating the supraoccipital from the frontals; opercular bones well developed. Vertebral centra well ossified, but always pierced by the notochord; ribs delicate; epipleurals present; no fused or expanded haemal arches at the base of the caudal fin. Dorsal and anal fins small, the former above or behind the ventrals. Ventrals with 5 to 10 rays. Scales thin, cycloid and deeply imbricate, usually coated with ganoin in their exposed portion.
Fig. 325.—Leptolepis dubius. (Restoration of skeleton by A. S. Woodward.)
Leptolepis, with numerous species, from the Jurassic and Cretaceous of Europe and New South Wales; Vidalia, Jurassic of France; Aethalion, Jurassic of Bavaria; Thrissops, Jurassic and Cretaceous of Europe; and Lycoptera, Jurassic of Asia.
Fam. 5. Elopidae.—Margin of the upper jaw formed by the praemaxillaries and the maxillaries, the latter the more developed, and movably articulated above the former to the ethmoid. Parietal bones in contact behind the frontals; opercular bones well developed. Basis cranii double. A bony intergular or sublingual plate. Jaws, palatines, pterygoids, vomer, parasphenoid, glossohyal, and pharyngeals toothed. Ribs mostly sessile, inserted very low down, behind parapophyses; epineurals similar to the ribs, but directed upwards. Pectorals low down, folding like the ventrals. Post-temporal forked, the upper branch attached to the epiotic, the lower to the opisthotic; post-clavicle small; scapular foramen in the scapula; pterygials well developed, three in contact with coracoid. Ventrals with 10 to 16 rays. Branchiostegal rays very numerous (over 20). Air-bladder large.
This family is abundantly represented in Cretaceous times by the genera Osmeroides and Elopopsis, and from the Lower Eocene to the present day by Elops and Megalops. Elops saurus is a handsome elongate silvery Fish, found in all the warm and tropical seas; the young are ribbon-shaped like those of Albula. A second species, E. lacerta, is from the West Coast of Africa, entering rivers. Megalops, distinguished by larger scales, the absence of pseudobranchiae, and the curious prolongation of the last ray of the dorsal fin, includes the well-known Tarpon M. atlanticus, and the Indian M. cyprinoides. The Tarpon occurs from the south-eastern coasts of North America and the West Indies to Brazil, and reaches a length of 6 feet and a weight of 110 lbs. It often leaps out of the water, after the manner of Grey Mullets, and its chase when hooked affords good sport, the landing of so active a giant being attended with great difficulties. Its remarkably large scales, over two inches in diameter, are much prized for fancy work in the Florida curiosity shops.