434 li.vxoiDEi. 



Second Suborder. BATOIDEI. 



Gill-openings ventral. In a few of the genera, 

 which we place first, the habit is still that of the 

 Sharks ; but the body is depressed ; and in the typical 

 genera the trunk, which is surrounded by the im- 

 mensely developed pectoral fins, forms a broad flat 

 disk, with a thin and slender tail. Spiracles always 

 present. Five pairs of gill-openings. No anal fin ; 

 dorsal fins, if present, on the tail. — Rays. 



Inhabitants of all the temperate and tropical seas; some species 

 exclusively pelagic ; others entering fresh waters, or entirely limited 

 to rivers within the tropics. 



Synojysis of the Families and Genera. 



Fam. 1. PRISTIDiE. 



Snout much produced, with lateral teeth, saw-like. 



Saw without tentacles 1- Pristis, p. 4.".n. 



Fam. 2. RHINOBATID^. 



Trunk gradually passing into the strong and long tail, which is 

 provided with two dorsal fins and a caudal. Pectorals not ex- 

 tending to the snout. 



Thft first dorsal opposite to the ventrals 2. Mhj/ncJiohafufi, p. 440. 



Dorsal fins at a great distance behind the ventrals ; anterior nasal valves 



not conHuent 3. Rhinobatus, p. 441. 



Anterior nasal valves confluent into a broad flap with free a margin. 



4. Tryf/miorhina, p. 447. 



Fam. 3. TORPEDINIDiE. 



Trunk a broad, smooth disk. Rayed dorsal and caudal fins 

 generally present. An electric organ. 



Tv^ dorsal fins ; ventrals separate ; spiracles at a short distance behind 

 the eyes 5. Torpedo, p. 44H. 



Two dorsal fins ; vfutrals scpnrati! ; spiracles immediately behind the 

 eyes ; lail longer than the disk (3. Nardiie, p. 452. 



Two dorsal fins. Tail extremely sn all and short. 



7. Ili/ptios, p. 453. 



Ventral fins luiiletl 8. J)iscopi/</e, p. 45.3. 



One ckn-snl flu only 0. Adrape, p. 454. 



Dorsal fins absent 10. Tcniera, p. 4.')5. 



