HETEROSCYMNUS LONGUS. 239 



Brown, light to dark, with a darker band around the neck, across the gill 

 openings: lower surfaces lighter to white, excepting perhaps the blackish collar 

 on the neck, the lower surfaces of body, head, pectorals, ventrals, and caudal are 

 luminous in life. 



Tropical and temperate seas. 



Heteroscymnus. 



Heleroscymnus Tanaka, 1912, Fishes of Japan, 6, p. 104. 



Body long, somewhat compressed; head depressed; tail short. Snout 

 pointed, nostrils near the end. Mouth nearly transverse, with a deep groove at 

 each angle. Teeth unlike: upper lanceolate, numerous; lower larger, com- 

 pressed, with an oblique triangular cusp. Gill openings moderate, in front of 

 the pectorals. Eyes small, without a nictitating membrane. Fins rather small; 

 no spine in front of dorsals; first dorsal above the postpectoral space; no anal 

 fin; caudals short and deep, no caudal pit. Scales of shagreen minute. 



Heteroscymnus longus. 



Heteroscymnus longus Tanaka, 1912, Fishes Japan, 6, p. 102, pi. 26. 



Subfusiform, head depressed, body compressed, caudal pedicel slightly de- 

 pressed. Body cavity about two thirds of the total length, head nearly one 

 fifth. Snout less than one third of the head, depressed and broadly blunted 

 across the end. Nostrils oblique, entirely in the forward half of the snout. Eye 

 small, diameter nearly one tenth of the distance from the snout to the first gill 

 opening; no nictitating membrane. Mouth inferior, below the eye, slightly 

 arched forward, with a deep straight groove across each angle extending backward 

 nearly one third of the distance to the gill opening. Upper teeth raptorial, many, 

 lanceolate, functioning in several series; lower much larger, compressed, sectorial, 

 non serrated, functional in two series, of eighteen teeth each (the outer series 

 acting more as supports or braces to the inner, and on the way to be dropped), 

 each tooth with a triangular, oblique cusp, outward directed from a notch in the 

 outer edge. No median tooth on the lower jaws. Spiracle small, oval, behind 

 the eye and at a higher level, its distance from the orbit nearly equal to that 

 between nostrils and orbit or nostrils and mouth. Dorsals, pectorals, and ventrals 

 small ; dorsals with hinder angle produced ; hind margin of first dorsal and sub- 

 caudal concave; origin of first dorsal little nearer to origins of pectorals than to 

 those of the ventrals; origin of second dorsal above ends of bases of ventrals, 



