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



the gill-laminse. Ventrals composed of several rays, slightly in advance of the pectorals, 

 which are narrow. Bones flexible ; mucous cavities of the head of moderate capacity. 

 Pseudobranchise none. 



Allied to Strinsia, but apparently with the dentition and fins modified. 



Melanonus gracilis (PI. XIV. fig. B). 



MeLanonus grwilis, Giinth., Ann. and Mag. Nat. Hist., 1878, ii. p. 19. 



B. 5. D. G I 67. A. 54. 3 D. + C. + 2 A. = 50. P. 10. V. 5. 



The head bears, as regards form and general configuration, a striking resemblance to 

 that oi Melamphaes ; it is of moderate length, equal to the distance of the root of the 

 ventrals from the vent, rather broad, and with the snout obtuse and arched down- 

 wards. Only the operculum and praeopercular limb are scaly ; the remainder is 

 covered with a soft skin, which is roughened by short, soft, keel-like prominences. 

 The portion covering the front of the snout between the nostrils is of a lighter 

 colour, with a network of low folds, and similar to the same organ in Melamphaes 

 typhlops. The muciferous channels are of moderate extent, and open by small but very 

 distinct pores in the usual manner. One pore, rather wider than the rest, opens in the 

 centre of the upper surface of the head. The eye is of moderate size, two-ninths of the 

 length of the head, and rather shorter than the snout. Interorbital space much wider 

 than the eye, convex. 



The mouth is wide, slightly oblique, and not reaching backwards to the hind margin 

 of the orbit, the maxillary being but little dilated at its posterior extremity. The jaws 

 are equal in front, or the mandible projects scarcely beyond the upper. 



Gill-membranes united below the isthmus for some distance, supported by short 

 branchiostegals. 



The trunk is compressed, passing into the tail, which tapers into an exceedingly 

 narrow extremity. Of the scales only a small portion has been preserv^ed ; they are 

 thin, deciduous, marked with numerous concentric striae, and of moderate size. There 

 seem to be two and a half in a transverse series between the first dorsal and the 

 lateral line. But the course of the latter cannot be traced, owing to the condition of 

 the specimen. 



The fin-rays are of very delicate structure, connected by a thin membrane, and the 

 posterior are so closely packed and so fragile that to count them is a matter of some 

 difficulty. All are more or less directed backwards, especially the posterior. 



The first dorsal begins above the root of the pectoral, and is much lower than the 

 body ; its longest rays are longer than those of the second fin, which maintain nearly the 

 same length to the end of the fin. The second fin commences immediately behind the 



