IV. No suborbital stay; basis cranii simple; a perforate scapula; three pterygials in contact with the coracoid; ventral fins thoracic; a suctorial laminated disk on the upper surface of the head .......... VI. Discocephali.
V. A suborbital stay, the second suborbital bone more or less produced on the cheek or joining the praeoperculum; ventrals thoracic .......... VII. Scleroparei.
VI. No suborbital stay; ventrals usually jugular or mental; if thoracic, structure of the pectoral arch differing from that ascribed to the first five divisions of this Synopsis.
Pectoral fin with vertical or subvertical base; anal fin usually elongate, rarely small .......... VIII. Jugulares.
Pectoral fin with horizontal or sub-horizontal base; body exceedingly compressed; dorsal fin with all the rays simple; anal fin absent or very small .......... IX. Taeniosomi.
Division I.—PERCIFORMES.
No bony stay for the praeoperculum. Basis cranii double. Spinous dorsal usually well developed. None of the epipleural bones attached to the centra of the vertebrae in the praecaudal region. Pectoral arch with well-developed scapula and coracoid, the former pierced by a foramen or fenestra; pterygials longer than broad, more or less regularly hour-glass-shaped, four or five in number, one or two of which are in contact with the coracoid. Ventral fins thoracic.
This large group, consisting chiefly of marine forms, has members in all parts of the world, with the exception of the Arctic and Antarctic regions, and was already represented by numerous Berycidae and a few Serranidae and Scorpididae in the Upper Cretaceous. The division into families is a task of considerable difficulty, and the necessities of a linear arrangement result in the breaking up of some natural sequences. Thus it appears highly probable that the Scorpididae, themselves derived, together with the Serranidae, from the Berycidae, lead to the Carangidae in the division Scombriformes, whilst a nearly perfect passage can be traced between the Acanthuridae of this division and the Balistidae among the Plectognaths.
Synopsis of the Families.
I. Gills four, a slit behind the fourth.