144 Mr. A. Alcock on a 
XVIII.—Natural History Notes from H.M. Indian Marine 
Survey Steamer ‘ Investigator,’ Commander C. F, Oldham, 
R.N., commanding.—Series II., No. 18. On a new Species 
of Viviparous Fish of the Family Ophidiide. By A. 
Aucock, Superintendent of the Indian Museum. 
Family Ophidiide. 
DIPLACANTHOPOMA, Giinther. 
Diplacanthopoma, Giinther, ‘ Challenger’ Deep-sea Fishes, p. 115. 
Diplacanthopoma Rivers- Andersoni, sp. n. 
The tail (caudal included) is not quite half, the head is 
considerably more than one fourth, the height of the body is 
about one fifth of the total length (caudal included). 
The head (including the branchiostegal rays and the greater 
part of the isthmus, but excluding the occiput), and also the 
greater part of the dorsal and anal fins, are invested ina thick 
glandular scaleless skin, which is of a much darker colour 
than, and is very definitely delimited from, the scaly covering 
of the body. The head is without any armature except the 
two sharp, flat, oblique spines, which project freely, one at 
the upper, the other at the lower angle of the operculum. 
The eye, which is about two thirds the length of the 
depressed snout and between one sixth and one seventh the 
length of the head, is sunk beneath thick transparent skin, 
without any orbital fold. 
The nostrils are situated one in front of the eye, the other 
near the tip of the snout, on either side. 
The mouth is large; the maxilla, which reaches a little 
behind the after limit of the eye, is half the length of the 
head, and is not overhung by the snout, but overlaps the 
mandible. Villiform teeth are present in bands on the jaws, 
vomer, and palatines, the bands on the jaws being rather 
widely interrupted at the symphyses. The tongue is short 
and broad and has only the tip free. 
The gill-openings are extremely wide; the branchiostegal 
rays are eight in number and their membranes are quite free ; 
there are three large lanceolate gill-rakers on the outer border 
of the first arch, but elsewhere the gill-rakers are tuberculi- 
form. There are no traces of pseudobranchie. 
The lateral line appears to have been present only on the 
anterior part of the trunk. 
The dorsal fin begins about an eye-length behind the level 
