FISHES. 203 



FAMILIES OF ACANTHOPTERL 



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



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



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



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



3. Tail ending in a sharp point ; no caudal nor ventrals ; teeth 



strong. . Trichiuridce, the Hair-Tails. 



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



sucking disk. . . . Echeneididce, the Remoras. 



5. Ventral fins completely united, sometimes forming a sucking 



disk. 



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



Dorsal single ; spinous dorsal enveloped in skin, forming a 



hump in the adult ; scaleless, tuberculate. 



CydopteridcB) the I/ump-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. Qobiesocidm, 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. . . . Carangidce, 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. 



