CCCIV 



with white exists on the side. Mouths of the Ganges, Irrawaddi, and 

 other large rivers, ascending far above tidal influence. 



395. Tetrodon fluviatilis, Ham. Buch. Two imperforate nasal 

 tentacles on either side. Body nearly smooth. Superiorly greenish- 

 yellow,with vermiculated blackish lines, becoming white below : there 

 are also irregular black spots and blotches. Large rivers of India and 

 Burma, far above tidal influence. 



396. Tetrodon patoca, Ham. Buch. Bheng-pulli, Ooriah : Nga-boo- 

 din, Burm. An imperforate nasal cavity with a fringed margin. Body 

 6piny. Light brown above with whitish spots, becoming silvery below. 

 Large rivers of India and Burma, far above tidal reach. 



Sub-class— CHONDROPTERYGII. 



Skeleton cartilaginous : no cranial sutures. Rarely a single 

 gill-opening, as the gills by their outer edges are attached 

 to the skin, and there exists an intervening gill-opening 

 between each : no gill-cover. Three series of valves at 

 the bulbus arteriosus. Optic nerves although united 

 do not decussate. Body with vertical and paired fins, 

 the posterior pair abdominal : caudal with an upper 

 lobe, which is elongated. Intestines with a spiral valve. 

 Male sex with prehensile organs attached to the vertical 

 fins. Ovaries containing large ova which are fertilised, 

 and in some likewise developed internally. Embryo with 

 external deciduous gills. No air-vessel. 



Order— PL A GIO STOMA TA. 



Body more or less cylindrical, or depressed : the trunk may or may not 

 pass into the tail. .From five to seven gill-openings, which may be 

 lateral or inferior. Jaws distinct from the skull. 



Sub-Order— SELACH01DEI, OR SHARKS. 



Body more or less cylindrical, gradually merging into the tail. 

 Gill-openings lateral. 



Family — Carch ARIID.E. 



The snout may be produced longitudinally (Carchariinse or true sharks) : or laterally 

 (Zyfsenina or hammer-beaded sharks). Spiracles absent or present Eye with 

 a nictitating membrane. A small pit may or may not exist above the root of the 

 tail, and a second bebind the angle of the mouth may be present or absent. Mouth 

 crescentic, inferior. Teeth may be erect or oblique, with a single cusp, hav- 

 ing sharp, smooth, or serrated edges : or they may be small, the cusps being 

 obsolete : or with one in the centre, or one or two lateral ones : or even obtuse. 

 The first dorsal fin, destitute of a spine, is placed opposite the interspace between 

 the pectoral and ventral : anal fin present. 



Genus — Carch arias, Hull, and Ilenle. 



No spiracles. A pit above the root of the caudal Jin. Snout longi- 

 tudinally produced. Mouth crescentic : the labial fold or groove rarely 



