46 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



opposite to each other on the tail, moderately long. Adipose fln none. Caudal forked. 

 Pectorals small. Ventrals none. The humeral arch terminates in the middle of the chest 

 in a long, projecting, acute spine. Gill opening 'wide; six branchiostegals. Gills very 

 narrow; pseudobrauchhe present; gill rakers lanceolate. Pyloric appendages rudimentary. 



PLATYTROCTES APUS, Gunther. (Figure 53). 



Platytroctea apus, Gunther, Ann. and Mag. Nat. Hist., 1878, u, 249; Challenger Report, xxn, 1887, 229, pi. 

 i. vm, fig. A. — Alcock, Ann. and Mag. Nat. Hist., vi, 1890, n. 307. 



Body much compressed and deep; its greatest depth at about the middle of its length, 

 and contained in it 2f times, not including the caudal. Head compressed, moderate, two- 

 sevenths of the length of the body, longitudinally concave above, the concavity bordered on 

 each side by a perforated muciferous canal, and broadest behind, tapering to a pointbetween 

 the nostrils. Bones of head are rather thin, but less so than in Bathytroctes. Bye large, 

 one-third of the length of the head, equal to snout, and situated close to upper profile. 

 Infraorbital ring incomplete. Mouth rather small, the lower jaw projecting. Maxillary 

 broad, short, extending to vertical from margin of orbit. Dentition very feeble ; teeth uni- 

 serial, uniformly minute, occupying the whole extent of intermaxillary and the maxillary, 

 but confined to the front part of the mandible; only a few rudimentary teeth are visible on 

 the side of the mandible. Vomer with a minute tooth on each side; palatines toothless. 



Branchiostegals extremely slender, curved. Gills four; the inner one very short; gill 

 lamime short, especially on the convex portion of the arches; gill rakers long, lanceolate, 

 • closely set, 20 + 10 on the outer branchial arch. 



Vent is much nearer to root of caudal than to gill opening. Dorsal tin commences 

 immediately above it, the anal behind; these fins are very similar in shape and of moderate 

 height. Caudal peduncle more than half as deep as long, its depth being increased by a 

 fold of the integument between the vertical fins. Caudal rather short and forked. Pecto- 

 ral very short, only half as long as the eye. 



Scales small, cycloid, each with a longitudinal keel, and not spinigerous, as in Maerunu, 

 but simple, as in the keeled scales of a snake; the striatums, instead of continually crossing 

 the scale, are interrupted by the raised median line. Head entirely scaleless. Lateral line 

 straight, running along the middle of the body and tail, and composed of very small pores. 



Brown; head, pectoral region, the vent, and fringes of the caudal peduncle black. 



Radial formula: D. 18; A. 17; P. 20; L. lat. about 100. 



A single individual, ~>i inches long, was taken by the Challenger at station 107, in the 

 middle Atlantic, at depth of 1,500 fathoms. Alcock records it from the Arabian sea, Investi- 

 gator station 105, in 740 fathoms. 



XENODERM1CHTHYS, Gunther. 



Xenodermichihys, Gunther, Ann. and Mag. Nat. Hist., n, 1878, 250; Challenger Report, xxn, 1887, 230. 

 Body rather elongate, compressed, withotit true scales. The skin is rather tough, finely 

 wrinkled longitudinally, with numerous small nodules, regularly arranged, which possess 

 the structure and probably the functions of luminous organs. Minute, rudimentary, scale- 

 like productions are imbedded in the skin, especially on the trunk. Month very small, with 

 feeble jaws and rudimentary teeth in the intermaxillary and mandible, and a few in the 

 maxillary. Palate toothless. Dorsal and anal fins equal in length. Caudal forked. Gill 

 opening wide, but not extending much above the level of the pectoral fins. Gills well 

 developed; pseudobranchise. Gill rakers long. 



XENODERMICHTHYS NODCLosrs, Gunther. (Figure 57.) 



Xenodermichthys nodulosus, Gunther, Ann. and Mag. Nat. Hist.. 1878. n, 250; Challenger Report, xxn, 230, 

 pi. lviii, fig. C. 



Body compressed, elongate, resembling the Stomiatids; its depth nearly uniform 

 between the head and vent, and contained 6J times in the total length. Head longer than 

 deep; its length 5^ in total. Snout short, obtuse, with parabolic anterior profile. Mouth 



