146 
Memoirs of the Indian Museum. 
[VoL. II, 
Colour black. 
One specimen measuring 13 cm. from the Bay of Bengal. Station 371, 500 
fathoms. Registered No. 
This genus must be closely related to Platytroctes. It is most interesting that 
the two genera should be separated by such a major character as a pair of pelvic fins 
and yet resemble one another so closely in minor details. The similarity of their 
outward appearance is most remarkable. 
The genus contains the species P.apus, Günther, and P. procerus, 
Brauer. The “ Investigator ” has obtained a single specimen of P. from near 
the Laccadive Isles. I have had the opportunity of comparing this with Platytroctegen. 
The main difference lies in the pelvic fins of the latter. With this is necessarily asso- 
ciated the fact that the contours of the body are not formed by empty skin as in 
Platytroctes, for pelvic fins could not be supported on a fold of empty skin. In Platy- 
troctes the highest and lowest quarter of the body will transmit light, for the com- 
ponent layers of skin are in contact with one another internally. In our specimen of 
P. apus only those scales which cover the empty folds of skin are keeled. The scales 
covering the middle or thick part of the body are not keeled. 
The specimen of Platytroctes apus obtained by the “ Investigator ” has a tubular 
papilla behind the operculum similar to that possessed by Platytroctegen. In both 
the system of muciferous canals on the head is as alike as though they were of the 
same species. Similarity in other features is equally great and yet the differences are 
very decided. Apart from the pelvic fins the following are the chief differences ; — 
1. The triangular cranium is depressed in the middle line in Platytroctes apus, 
— nearly flat in Platytroctegen. 
2. The scales are keeled like those of a reptile in Platytroctes apus, — smooth 
in the other. In our specimen of P. apus only the upper and lower scales 
are keeled. 
3. The remarkable clavicular spine is bifid at the tip in Platytroctes , — simple in 
the other. 
4. The dorsal and anal fins are longer in Platytroctegen. 
P. procerus is also furnished with the postopercular papilla. It is likely that the 
first example of P. apus which was taken by the ‘‘ Challenger ” in the Atlantic Ocean 
also possessed a similar organ which became detached or was otherwise overlooked. 
Alepocephalus microlepis, sp. nov. 
Illustr. Zool. ‘'Investigator Fishes, plate xliv, fig. 4 (1909). 
B. 6, D. 20-22, A. 30-33, V. 5-6, P. 10, Iv.l. 125, L.tr. 30-35. 
The head is slightly less than a third of the total without the caudal. The maxi- 
mum height — which is at the base of the pectoral fin — is a sixth of the total. The vent 
is nearer to the gill-opening than to the base of the caudal fin. The ventrals are 
much nearer to the vent than to the gill-opening. The anal fin, being much longer 
