188 

 150. Halosaurus nigerrimus, Alcock. 



Halosaurus nigemmns, Alcock, Ann. Mag. Nat. Hist., Aug. 1898, p. 149 : Illustrations of the Zoologt of 

 the Investigator, pl. XXXIII. fig. 2. 



B. 12. D. circ. 12. P. circ. 9. V. 8. 



Temples and cheeks scaly; head otherwise naked. Length of the head 

 about a seventh of the total and nearly equal to the distance between the 

 gill-opening and the base of the ventral fin. Length of the snout about 2- 

 in that of the head ; about a third of its extent is preoral. Eyes about two- 

 thirds of a diameter apart. 



The maxilla reaches to the anterior edge of the pupil. 



Teeth as in H. carinicauda. 



Numerous long close-set gill-rakers on the outer side of the first branchial 

 arch. 



Scales deciduous : those of the lateral line adherent and much enlarged and 

 about 30(?) in number between the gill-opening and the vent. There is a low 

 median fold of skin, with some enlarged scales, behind the dorsal fin, as in 

 H. carinicauda. 



Fins as in H. carinicauda, but the ventrals are united with one another only 

 in their basal portion. 



Colour : everywhere uniform jet black. 



One young specimen about 7 5 inches long, from off the Maldives, 459 

 fathoms. 



Regd. No. if. 



Family Muraenidce. 



To the ten genera and thirty-nine species recorded in the Fauna of British 

 India, the " Investigator " has added other ten genera and seventeen species. 



Key to the Indian Deep Sea genera of Muraenidie. 



The branchial openings into the pharynx are wide slits : the heart is 

 situated between or close behind the gills : — 



1. Vent close to the gill-opening : nostrils close together in a hollow in 

 front of the eye : jaws produced to form a long slender beak : 

 NEMICHTHYTNA :— 



i. Pectorals present, the vent being between their roots ... Nemichthys. 



ii. Pectorals absent : vent about a snout length behind the gill- 

 opening ... ... ... ... ... Gavialiceps. 



2. Vent at no great distance from the gill-opening : nostrils distant from 

 one another, lateral : snout not beak-like : eyes small : DYSOM- 

 MINA:— 



i. Pectorals present, the vent being between their roots ... Dysomma. 



