FISHES. 203 



FAMILIES OF ACANTHOPTERL 



1. With 5 to 9 detached finlets behind dorsal and anal ; dorsals 



two ; scales small or none. . Scombridce, the Mackerels. 



2. Upper jaw prolonged into a " sword " ; teeth feeble or wanting ; 



scaleless ; size large. . . Xiphiidce, the Sword-Fishes. 



3. Tail ending in a sharp point; no caudal norventrals; teeth 



strong Trichiuridce, the Hair-Tails. 



4. First dorsal on the top of head, modified into a lamellated 



sucking disk. . . . Echeneididce, the Rem&ras. 



5. Ventral fins completely united, sometimes forming a sucking 



disk. 



Dorsals two, distinct ; body scaly or not. . GOBITIXE, 96. 



Dorsal single ; spinous dorsal enveloped in skin, forming a 



hump in the adult ; scaleless, tuberculate. 



Cydopteridce, the Lump-Suckers. 



Dorsal single ; body elongated ; scaleless ; small fishes often 



parasitic in shells of Mollusks. Liparididce, the Sea Snails. 



6. Ventral fins wide apart, with a sucking disk between them ; 



dorsal spineless, on the tail. Gobiesocidte, the Pike-Suckers. 



7. With a stout, sharp spine on each side of tail ; body much com- 



pressed. .... Acanthuridce, the Surgeons. 



8. With several unconnected spines in place of the first dorsal. 



Tail with a keel on each side. Carangidce, the Pilot Fishes. 



Anal fin preceded by two free spines ; body compressed and 



elevated. . . . Carangidcs, the Pilot Fishes. 



Tail not keeled; jaws toothless; body very long and slender. 



Ammodytidce, the Sand Launces. 



Tail without a keel ; jaws with teeth. 



Body long ; snout elongated. Elacatidce, the Crab-Eaters. 

 Body short, compressed ; snub-nosed. 



Stromateidce, the Harvest Fishes. 



9. With none of the preceding combinations. 



* With two distinct dorsal fins rarely slightly connected by 



membrane at the base. 

 f Body with developed scales or bony plates, large or small. 



