118 THE VOYAGE OF H.M.S. CHALLENGER. 



of which are two-fifths as long as the head. The ventral filaments are about half the 

 length of their distance from the vent. 



The entire fish is either black or of a reddish-white colour, with the exception of the 

 jaws and abdomen, which, like the buccal and branchial cavities, are of a deep black, as is 

 so often the case in deep-sea fishes. 



Distance of the snout from the eye. 



Distance of the snout from the gill-opening, 



Distance of the snout from the vent, 



Total length, ..... 



Habitat. — Philippine Islands, Station 205 ; depth, 1050 fathoms. One specimen, 

 13 inches long. 



North of New Guinea, Station 218; depth, 1070 fathoms. One specimen, 11| 

 inches long. 



Of the figures on PL XXIV. figure a represents the outer and figure a' the inner 

 aspect of the first branchial arch. 



Typhlonus. 

 Typhlonus, Giinth., Ann. and Mag. Nat. Hist., 1878, vol. ii. p. 21. 



Head large, compressed, with most of the bones in a cartilaginous condition ; the 

 superficial bones with enormous muciferous cavities, not armed. Snout a thick pro- 

 tuberance, projecting far beyond the mouth, which is rather small and inferior. Trunk 

 very short, the vent being below the pectoral ; tail excessively compressed, deep, tapering, 

 without separate caudal. Eye not visible externally, reduced to a minute rudiment 

 hidden below the skin. Bands of villiform teeth in the jaws, on the vomer and palatine 

 bones. Barbel none. Veutrals reduced to simple filaments, placed close together on 

 the humeral symphysis. Gill-openings very wide, the gill-membranes being but 

 slightly united in front. Gills four ; gill-laminse very short, gijl-rakers of moderate 

 length. Scales thin, deciduous, small. /' 



A true deep-sea form. 



After removal of the extremely thin skin from the side of the head, a partly cartila- 

 ginous partly membranaceous layer is laid bare, which is formed by the greatly expanded 

 dermal bones and the walls of the mucous cavities. The place of the orbital cavity is 

 covered by this layer, underneath which a minute black globular body (smaller than 

 a pin's head) represents the rudiment of an eye. The opercular bones are almost 

 membranaceous, the sub- and interoperculum supported by fibrous rays. Vertebrae 

 thin, but ossified. The abdominal cavity does not extend into the tail. Liver small. 

 Stomach apparently not much distensible, covered by a lamina of the black peritoneum. 



