FISHES. 203 



FAMILIES OF ACANTHOPTEKI. 



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

 two; scales small ornone. . Seomiridm, the Mackerels. 



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

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



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



strong. .... TricMv/ridm, the Hair-Tails. 



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



sucking disk. . . . Eeheneidida, the Bemoras. 



5. Ventral fins completely united, sometimes forming a sucking 



disk. 



— Dorsals two, distinct; hody scaly or not. . GoBiiD.a!, 96. 



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



hump in the adult; scaleless, tuberculate. 



OyclopteridcB, the Lump-Sudcers. 



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



parasitic in shells of Mollusks. Lipa/rididce, the Sea Snails. 



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



dorsal spineless, on the tail. Gobiesocidm, 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. Gwrangidm, the Pilot Fishes. 



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



elevated. . . . Owra/ngidm, the Pilot Fishes. 



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



Ammodytidm, the San^d Launces. 



— Tail without a keel ; jaws with teeth. 



Body long ; snout elongated. Elacatidm, the Grah-Eaters. 

 Body short, compressed ; snub-nosed. 



StromateidcB, the Ma/reest 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. 



