In the classification of Günther, which has been generally in use in this country for the last thirty years, the Teleosts were divided into six principal groups, of ordinal rank: I. Acanthopterygii; II. Acanthopterygii Pharyngognathi; III. Anacanthini; IV. Physostomi; V. Lophobranchii; VI. Plectognathi. Group I. corresponds to Sub-Order 6 (part), 7 (part), 8 (part), 10 (part), 11 and 12 of the present work; Group II. to Sub-Order 10 (part); Group III. to Sub-Order 9 and 10 (part); Group IV. to Sub-Order 1, 2, 3, 4, 5, 6 (part), and 8 (part); Group V. to Sub-Order 7 (part); and Group VI. to Sub-Order 13.
Sub-Order 1. Malacopterygii.
Air-bladder, if present, communicating with the digestive tract by a duct. Opercle well developed. Pectoral arch suspended from the skull; mesocoracoid arch present.[[641]] Fins without spines, the ventrals abdominal, if present. Anterior vertebrae distinct, without Weberian ossicles.
This sub-order, which corresponds to the Isospondyli and Scyphophori of Cope and to a part of the Isospondyli of A. S. Woodward, embraces the most generalised of the Teleosts, and is intimately connected with the Ganoids by the fossil forms which are placed at the base of the series of families. The physostomous condition of the air-bladder, the connexion of the pectoral arch with the skull, the presence of the mesocoracoid arch, the backward position of the many-rayed ventral fins, the normal condition of the anterior vertebrae, the absence of true spines to the fins, and the separation of the supraoccipital bone from the frontals by the parietals, are primitive characters which among the Teleosts occur combined in some families of this suborder only. The mesocoracoid arch is retained by the Ostariophysi, which differ in the remarkably modified condition of the anterior vertebrae, but it disappears in all other Teleosts, which gradually acquire a more forward position of the ventral fins and a reduction in the number of their rays, develop spines in the vertical fins, and lose the communication of the air-bladder with the outside.
The Malacopterygii may be divided into twenty-one families, the characters of which are contrasted in the following synopsis:—
I. Fins fringed with fulcra, or scales coated with ganoin; notochord usually continuous through the vertebrae.
Vertebral centra not more than rings; fins with fulcra; scales rhombic, united by peg-and-socket joints .......... 1. Pholidophoridae.†
Vertebral centra not more than rings; fins with fulcra; scales cycloid .......... 2. Archaeomaenidae.†
Vertebral centra complete or with minute perforation; fins with fulcra; scales cycloid .......... 3. Oligopleuridae.†