A. Epipleurals present.
1. Second suborbital produced inwards to support the eye-ball.
Ventrals close together; scales very small, cycloid, forming oblique bands .......... 1. Trachinidae.
Ventrals widely separated .......... 2. Percophiidae.
2. No subocular shelf.
Ventrals widely separated; two nostrils on each side .......... 3. Leptoscopidae.
Ventrals widely separated; a single nostril on each side .......... 4. Nototheniidae.
Ventrals close together; scales very small, forming oblique bands; head partly covered with bony plates .......... 5. Uranoscopidae.
B. No epipleurals.
Post-temporal forked, articulated to the skull; soft dorsal and anal much elongate .......... 6. Trichodontidae.