1. Pelvic bones usually connected with scapular arch; spinous dorsal represented by isolated spines.
Snout conical or but slightly tubiform; ventral fins with 1 spine and 1 or 2 soft rays; ribs slender, free; anterior vertebrae not enlarged .......... 2. Gastrosteidae.
Snout tubiform; ventral fins with 1 spine and 4 soft rays; ribs flattened, fused with the lateral bony shields; anterior vertebrae not enlarged .......... 3. Aulorhynchidae.
Snout tubiform; ribs slender, free; first vertebra enlarged .......... 4. Protosyngnathidae.
2. Pelvic bones not connected with scapular arch; ventrals without spine, with 5 or 6 rays; snout tubiform; first vertebra very elongate, formed by the fusion of several.
Isolated dorsal spines; body scaly .......... 5. Aulostomatidae.
No dorsal spines; body naked .......... 6. Fistulariidae.
B. Mouth toothless; snout tubiform; two short dorsal fins, the first with a few spines; ventral fins with 3 to 5 rays; anterior vertebrae elongate.
Body covered with bony shields and small rough scales .......... 7. Centriscidae.
Body completely cuirassed by bony shields which are fused with the endoskeleton .......... 8. Amphisilidae.