COMPENDIUM OF GENERIC DISTINCTIONS. 



615 



Family. PROTONOPSIDJE — Legs strong. Teeth of palate 

 set across in an arched series. 



Genus. Protoxopsis. — As family. North America. 



Family. AMPHIUMIDiE.— Legs weak. Teeth of palate in 

 double diverging series. 



Genus. Ampwuma. — Two toes on each foot. North America. 



Genu*. Mru.KNoi'sis. — Three toes on eaeh foot. North 

 America. 



Order. PSEU DOPH I Dl A.— Body snake-like. No legs. Skin 

 smooth and wrinkled, with minute imbedded scales. 



Genus. C.kcii.ia. — A pit under each nostril. Africa and 

 South America. 



Order. PSEU DOICTHYAS.— Body fish-like, covered with 

 strong overlapping oval scales. Fur-like membranes, strength- 

 ened with soft jointed rays, above and below. Legs four, rudi- 

 mentary. Gill external. Teeth of palate and lower jaw very 

 large. 



Genus. Lepidosikkx. —Fifty-five pairs of ribs. Brazil. 

 Genus. Protopterus. — Thirty-six pairs of ribs. Gambia. 



Order. M EANTI A.— Body long, smooth, and naked. Legs 

 two or four, weak. Gills external and permanent. Teeth on 

 palate and lower jaw. 



Family. PROTEIDJE.— Legs four; tail compressed. Single 

 series of teeth on front edge of vomer. 



Genus. Proteus. — Head long. Three toes on fore feet, four 

 on hinder. Carniola. 



Genus. Nkcturus. — Head broad and compressed. Four toes 

 on all the feet. Mississippi. 



Fa, eilii. SIRENIDJE — Limbs two in front. Body nearly 

 cylindrical. Teeth in each jaw and on vomer in numerous 

 cross series. 



Genus. Siren". — Four fingers. Gills with cilia. North 

 America. 



CLASS.-FISHES. 



Vertebrated animals respiring through gills, living in water — Heart with one auricle and one ventricle ; blood 



cold and red- 



Order. CHONDROPTERYGII.—Skeleton cartilaginous. No 

 sutures in skull. 



Sub-order. ELEUTHEROPOML— Gills free. 



Family. ACIPENSERIDJE.— Head and skin covered at inter- 

 vals with cartilaginous or bony shields. 



Genus. AciPKXSER. — Nose conical and tapering; mouth under 

 muzzle, with beards. Eyes and nostrils at side. Body with 

 series of bony plates. Single dorsal fin, behind ventral and over 

 anal. Short under lobe to tail tin. Many parts of world. 



Genus. Scaphiorhynchhs. — Nose flat, convex above, eon- 

 cave below. Mouth beneath, with four beards. Five series of 

 scales on body. North America. 



Family. POLYODONTIDJE — No tubercles or plates on body. 



Genus. Pot.yoiiox. — As family. North America. 



Family. CHIMffiRID^. 



Genus. Chim.era. — Beak conical. Dorsal tins nearly contig- 

 uous. Northern seas. 



Genus. Calliorhyxchus. — Beak ending in leaf-like append- 

 age. Dorsals far apart. Southern seas. 



Sub-order. TREMATOPNEA.— Gills fixed by their edges to 

 bars across the openings. 



Sub-section. Squall- — No frontal cartilage on skull. Gill- 

 openings at sides. 



Family. SCYLLIDffi. — Body long, nearly cylindrical. Pecto- 

 ral tins moderate. Spout-boles. Gill-openings five, the last 

 being over the root of the pectorals. Tail not forked; under 

 iobe slight. 



Genus. Srvu.n \i. — First dorsal between ventral and anal; 

 second between anal and tail. Spiracles behind eyes, 



Genus. Pristidurds. — Snout long. Row of flattish prickles 

 on upper rim of tail. Many seas. 



Family. SQUALID-S:.— Body tapering to tail. Dorsals one or 

 two, first between pectoral and ventral. 



Genus. Sciuvr.rs. — Snout flat and rounded; nostrils in the 

 middle, between the mouth and the point of the snout. 



Genus. Spuvrxivs. — Head hammer or heart-shaped, with the 

 eyes at each side. Many seas. 



Genus. Galeus. — Head flat, spiracles small. Upper lobe of 

 tail with one or two notches. Many seas. 



Genus. MrsTEi.rs. — Spiracles large. Teeth mosaic-like. 

 First dorsal nearly in centre, tail short. Many seas. 



Genus. Isrars. — Gill-openings large and before pectorals. 

 Tail keeled on each side and crescent-shaped. Spiracles very 

 small, far behind eyes. Teeth flat and three-sided. Many seas. 



Genus. C arch vRonox. — Teeth three-sided, with notched 

 edges. Many warm seas. 



Genus. Cktorhinus. — Snout short and blunt. Gill-openings 

 very large, spiracles small. Teeth minute, conical, points di- 

 rected backward. Skin covered with little pointed scales. 

 Northern seas. 



Genus. Alopias. — Snout short and conical. Gill-openings 

 small, the last set over the pectorals. Teeth flat, three-sided, 

 not notched. Upper lobe of tail very long, with a little pit at 

 the root. Many seas. 



Genus. Ac'axthias. — A sharp spine before each dorsal. Head 

 flat. Spiracles large. First dorsal between pectoral and ven- 

 tral, ami second between ventral and anal. Many seas. 



Genus. Dat.atias. -No spines before dorsals. Head flat or 

 compressed. Spiracles behind eyes. Gill-openings small. No 

 I pit at root of tail. Many seas. 



