FISHES. 203 



FAMILIES OF ACANTHOPTERI. 



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



tW''">; scales small or none. . Scombndw, the Mackerels. 



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



scaleless ; size large. . . Xiphucke, the Sicord-Fishes. 



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



strong. . . . . THcMuridm, tlie Hair-Tails. 



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



sucking disk. . . . Echeiieididoi^ the Remoras. 



5. Ventral fins completely united, sometimes forming a sucking 



disk. 



— Dorsals two, distinct ; body scaly or not. . Gobiid^, 96. 



— Dorsal single ; spinous dorsal enveloped in skin, forming a 



hump in the adult ; scaleless, tuberculate. 



Cyclopteridm, the Lump-Suckers. 



— Dorsal single ; body elongated ; scaleless ; small fishes often 



parasitic in shells of Mollusks. Liparididce, the 8ea Snails. 



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



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



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



pressed. .... AcanthuridcB, the Surgeons. 



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



— Tail with a keel on each side. Ca-rangidce, the Pilot Fishes. 



— Anal fin preceded by two free spines ; body compressed and 



elevated. . . . Garangido}, the Pilot Fishes. 



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



Ammodytidm^ the Sand Launces. 



— Tail without a keel ; jaws with teeth. 



Body long; snout elongated. Elacatida;, the Crab-Faters. 

 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. 



