COMPENDIUM OF GENERIC DISTINCTIONS. 



779 



Genus. LEPIDOSIREN. Fifty-five pairs of ribs. Brazil. 

 Genus. PROTOPTERUS. Thirty-six pairs of ribs. Gambia. 



Order. MEANTIA. Body long, smooth, and naked. 

 Logs two or four, weak. Gills external and permanent. 

 Teeth on palate and lower jaw. 



Family. PROTEID-ffi. 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. Camiola. 



Genus. NECTURUS. Head broad and compressed. Foui 

 toes OP all the feet. Mississippi. 



Family. SIRENID^E. 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. 



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



cold and red. 



POLYODONTIDJE. No tubercles or plates on 



Order. CHONDROPTERYGII. Skeleton cartila- 

 ginous. No sutures in skull. 



Siib-order. ELEUTHEROPOML Gills free. 



Family. ACIPENSERID.ffi. Head and skin covered at 

 Intervals with cartilaginous or bony shields. 



Genus. ACIPENSER. Nose conical and tapering ; mouth 

 under muzale, 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 fin. Many parts of 

 world. 



Genus. SOAPHIORHYNCHUS. Nose fiat, convex above, 

 concave below. Mouth beneath, with four beards. Five 

 series of scales on body. North America. 



Family. 

 body. 



Genus. POLYODON. As family. North America. 

 Family. CHIMJERID.. 



Genus. CHIMERA. Beak conical. Dorsal fins nearly 

 contiguous. Northern seas. 



Genus. CALLIORHYNCHUS. Beak ending in leaf-like 

 appendage. Dorsals far apart. Southern seas. 



Sub-order. TKEMATOPNEA. Gills fixed by their edges 

 to bars across the openings. 



Sub-section. SQUALL No frontal cartilage on skull. 

 Gill-openings at sides. 



Family. SCYLLIDJE. Body long, nearly cylindrical. 

 Pectoral fins moderate. Spout-holes. Gill-openings five, 

 the last being over the root of the pectorals. Tail not 

 forked ; under lobe slight. 



Genus. SCYLLIUM. First dorsal between ventral and 

 anal ; second between anal and tail. Spiracles behind eyes. 



Genus. PRISTIDURUB. Snout long. Eow of flattish 

 prickles on upper rim of tail. Many seas. 



Family. SQUALID^!. Body tapering to tail. Dorsals 

 one or two, first between pectoral and ventral. 



Genus. SQUALUS. Snout flat and rounded ; nostrils in 

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



Genus. SPHYRNIAS. Head hammer or heart-shaped, 

 with the eyes at each sido. Many seas. 



Genus. GALEUS. Head flat, spiracles small. Upper 

 lobe of tail with one or two notches. Many seas. 



Genus. MuSTELtrs. Spiracles large. Teeth mosaic-like. 

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



Genus. ISURUS. 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. 

 Munv seas. 



Genus. CARCHARODON. Teeth three-sided, with notched 

 edges. Many warm seas. 



Genus. CETORHINUS. Snout short and blunt. Gill- 

 openings very large, spiracles small. Teeth minute, conical, 

 points directed 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. ACANTHIAS. A sharp spine before each dorsal. 

 Head flat. Spiracles large. First dorsal between pectoral 

 and ventral, and second between ventral and anal. Many 

 seas. 



Genus. DALATIAS. No spines before dorsals. Bead 

 flat or compressed. Spiracles behind eyes. Gill-openings 

 small. No pit at root of tail. Many seas. 



Family. SQUATINID./E. Body flat ; eyes on upper part 

 of head. Spout-holes very large, and behind eyes. Pectorals 

 greatly expanded in front. 



Genus. SQTJATINUS. As family. Many seas. 



Sub-section. RAH. Body flat ; spiracles. Gill-apertures 

 five, set before ventrals and under pectorals. 



Family. PRISTINID.23. Snout prolonged into a saw-like 

 form, with teeth on each edge. Skin covered with mosaic 

 scales. 



Genus. PRISTIOPHORUS. Beak with hooked spines of 

 various lengths, prickles attached to skin. Long barbel 

 under snout, and a keel on either side. Australasian seas. 



Genus. PRISTIS. Teeth of saw straight, similar, and 

 somewhat lancet-shape. Teeth flat and mosaic. Tail-fin 

 short. Many warm seas. 



Family. RAID./E. Body very flat and broad, with 

 slender tail. 



Genus. TORPEDO. Disc round and blunt in front ; back 

 rounded and naked ; tail-fin three-cornered. Teeth pointed 

 and attached to a cartilage. A row of tooth-like projections 

 on edge of spiracles. Warm and temperate seas. 



Genus. RAIA. Snout pointed and keeled, disc broad, 

 tail very slender. Teeth mosaic-like; in males pointed 

 during breeding season. 



Genus. TRYGON. Tail armed with one or more barbed 

 spines, and as long or longer than the body. Teeth either 

 pointed or wrinkled in the middle. Most seas. 



Genus. MYLIOBATIS. Teeth large, six-sided, mosaic. 

 Tail very long, slender, and with a powerful spine. Nostrils 

 close together in middle of snout. Warm seas. 



Genus. CEPHALOPTERA". Mouth at end of snout, and 

 very broad ; teeth small, flat, and leaf-like in lower jaw ; 

 none in the upper. Head with horn-like projections of the 

 fins. Tail very long, and with a spine. Many seas. 



