Fam. 13. Stephanoberycidae.—This Family has hitherto been placed near the Berycidae, among the Acanthopterygii, but there are no spinous rays in the dorsal and anal fins; and the ventrals, formed of one simple and four or five branched rays, are abdominal. The genus Stephanoberyx, with two species from the Atlantic, at depths of 535 to 2949 fathoms, is characterised by a large, thick, cavernous head, with thin bony spine-bearing ridges, a large mouth bordered by the protractile praemaxillaries, behind which are the large maxillaries, a short dorsal and a short anal, opposed to each other behind the ventrals, and the body covered with feebly imbricated scales, each bearing in the centre one or several erect spines. The largest specimen measures 6 inches. Malacosarcus, a small Fish from the Pacific, at depths of 2350 and 2425 fathoms, is very closely allied to Stephanoberyx, but its scales are very thin and cycloid. The striking resemblance which the head bears to that of the Berycid Melamphaes may be merely a case of convergence, and it must be borne in mind that this appearance is approached by some species of Scopelus, with which both Malacosarcus and Melamphaes were originally confounded. The praecaudal vertebrae are provided with parapophyses. I have ascertained on a specimen of Stephanoberyx monae that the air-bladder is connected with the dorsal side of the stomach by a short and comparatively wide duct.
Fig. 377.—Stephanoberyx gillii, nat. size. (After Goode and Bean.)
Fam. 14. Percopsidae.—Margin of the upper jaw formed by the praemaxillaries; mouth small, not protractile, toothed; palate toothless. Supraoccipital in contact with the frontals, separating the small parietals. Basis cranii simple. Most of the praecaudal vertebrae with parapophyses, on the upper surface of which the ribs are inserted; no epipleurals. Post-temporal forked; post-clavicle present; scapular foramen in the scapula, on which three hour-glass-shaped pterygials are inserted, a fourth being inserted on the coracoid. Dorsal fin with two true spines; anal with one or two; ventrals far forward, with 9 rays; pectorals inserted rather high. A small adipose dorsal fin. Body covered with strongly ctenoid scales. Air-bladder present (with open duct).
This is a most interesting group of Fishes, from the resemblance which they bear to the Perches, and they have therefore been raised to the rank of a sub-order, Salmopercae, by Jordan and Evermann, who regard them as "archaic fishes, relics of some earlier fauna, and apparently derived directly from the extinct transitional forms through which the Haplomi and Acanthopteri have descended from allies of the Isospondyli [Malacopterygii]." On the other hand, an analysis of their characters shows them to belong to the Haplomi, of which they may be regarded as highly specialised members, having evolved in the direction of the Acanthopterygii.
Only two genera are known, each with a single species: Percopsis, from the rivers and streams of Canada and the north-eastern United States, and Columbia, more recently discovered in the sandy or weedy lagoons along the Columbia River. These Fishes are of small size, not exceeding 6 inches in length. Their eggs are unusually large.
Fig. 378.—Columbia transmontana, natural size. (After Eigenmann.)
Sub-Order 6. Heteromi.
Air-bladder without open duct. Opercle well developed; parietal bones separating the frontals from the supraoccipital. Pectoral arch suspended from the supraoccipital or the epiotic, the post-temporal small and simple or replaced by a ligament; no mesocoracoid. Ventral fins abdominal, if present.