Ribs attached to the extremity of much-developed parapophyses; lower pharyngeal bones completely united; pectoral fins inserted very high up .......... 1. Scombresocidae.
Ribs mostly sessile; lower pharyngeal bones distinct; pectoral fins nearer the ventral than the dorsal line .......... 2. Ammodytidae.
II. Ventral fins, if present, more or less approximated to the pectorals.
A. Two well-developed dorsal fins, the anterior small and formed, at least in part, of spinous rays.
1. Ribs attached to strong parapophyses.
Pelvic bones free or connected with the clavicles by ligament; pectoral fins inserted high up .......... 3. Atherinidae.
Pelvic bones suspended from the postclavicles; pectoral fins inserted very high up; teeth very feeble or absent .......... 4. Mugilidae.
Pelvic bones suspended from the postclavicles; pectoral fins low down, with detached lower rays .......... 5. Polynemidae.
Pelvic bones connected with the clavicles by ligament; pectoral fins nearer the ventral than the dorsal line; dentition powerful, cardiform; scales minute or absent .......... 6. Chiasmodontidae.
2. Anterior ribs sessile; pelvic bones not connected with the scapular arch; pectoral fins nearer the ventral than the dorsal line .......... 7. Sphyraenidae.