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



Aphijonus. 

 Aphyonus, Giinth., Ann. and Mag. Nat. Hist., 1878, vol. ii. p. 22. 



Head, body and tapering tail strongly compressed, enveloped in a thin, scaleless, loose 

 skin. Vent far behind the pectoral in nearly the middle of the total length. Snout 

 swollen, projecting beyond the mouth, which is wide. No teeth in the upper jaw ; small 

 conical teeth in the lower, pluriserial in front and uniserial on the side. Vomer with 

 a few rudimentary teeth ; palatine teeth none. Nostrils close together, small. No 

 externally visible eye. Barbel none. Ventrals reduced to simple filaments, placed close 

 together, and near to the humeral symphysis. Gill-membranes not united. Four 

 branchial arches, the posterior without gill-laminae ; the anterior with very short gill- 

 rakers and with rather short gill-laminae. Head covered with a system of wide muciferous 

 channels and sinuses, the dermal bones being almost membranaceous, whilst the others 

 are in a semicartilaginous condition. Notochord persistent, but with a superficial 

 indication of the vertebral segments (as in some Leptocephaline forms). 



Although this fish resembles Typhlomis in so many points that one might be induced 

 to regard it as an early stage of development of that fish, no such direct relation can 

 obtain between them. The single individual obtained by the expedition has the ovaries 

 fully developed, filling one-half of the abdominal cavity, the ova being apparently mature 

 and ready for exclusion. It is, therefore, a persistent and independent t)rpe, the lowest of 

 all Anacanths, so far as is known at present, which has remained stationary at an early 

 stage of its development. The abdominal organs do not show any peculiarity, and are 

 very similar to those of Typldonus. 



Aphyonus gelatinosus (PI. XXVL fig. A). 



Aphyomts gelaiinosus, Guntb., Ann. and Mag. Nat. Hist., 1878, vol. ii. p. 22. 



The head, in the preserved specimen, is compressed, rather deep, and enveloped in 

 loose skin ; especially on the upper side of its anterior half the skin forms a large loose 

 bag, which, during life, is proba1)ly filled and distended with mucus. 



The snout overlaps the wide mouth, the maxillary extending backwards nearly to 

 the middle of the length of the head. A rudiment of the eye, in the shape of a minute 

 black globular body, is hidden below the skin in a recess of the infraorbital mucous sinus, 

 as in TypJdonus. Seen from above, the head appears convex, rather bruad ; its length 

 is less than its distance from the vent and one-fourth of the total. 



The body is strongly compressed and deep, its depth at the beginning of the dorsal 

 fin being one-third of the distance of the vent from the snout ; also the tail is deep and 

 short, shorter than the rest of the body. The skin covering the muscular parts is not 

 loose, very thin, transparent, so tliat the myocommas can be clearly seen through it. 



