128 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



the intermaxillary anil maxillary, each of which bears a row of long, recurved teeth at a con- 

 siderable distance from one another; mandible with a similar row, one of which on either 

 side is much more developed ; two scries of phosphorescent spots along the lower side of the 

 head, body, and tail." 



The type species, S. amabilis, Ogilby, was described from three mutilated specimens 

 picked up dead on the beach at Lord Howe's Island. 



The following brief statement of diagnostic characters is given by Ogilby. 



Height of body, three-fifths of total length. Least height of pedicle, about one-tenth 

 of height of body. Length of snout, about one half of diameter of eye. Colors, silvery. 



Radial formula: D. 5, 11-12; A. 13 (?); V. ('?); P. 10 (?); C. 6, 18, 6 ( !). 



POLYIPNUS, GUnther. 



Polyipnus, Gunther. Challenger Report, xxn, 1887, 170, (type, P. spinosus, from the surface near the Philippine 



Islands.) 



Polyipnus differs from Sternoptyx in having the body covered with very large anterior 

 scales and in lacking the anterior spinal dilatation of the anal fin. Its body is more reg- 

 ular in form, there being no deep indentation at the base ot the tail; and there are other 

 salient characteristics, chief among them the extraordinary development of the luminous 

 organs in size and number, not less than 55 phosphorescent organs on each side. 



The type of this genus is Polyipnus spinosus (Fig. 149), obtained by the Challenger 

 between the Philippine Islands and Borneo at a depth of 250 fathoms (GUnther, Challenger 

 Report xxn, 170, pi. li, fig. B.) and by the Investigator in the Bay of Bengal 188-210 fath- 

 oms. It differs from Sternoptyx in having the body a more regular shape, there being no 

 deep indentation by which the tail is separated from the trunk, and in other characteristics 

 described by Gimther. 



FAMILY IDIACANTHID^E. 



Idiacanthidce, Gill, Ms. 



Malacopterygians, with spiny processes from anterior portion of vertebra? projecting 

 through the skin of the body. Pectorals absent. Body naked. Dorsal fin beginning in 

 advance of the vent. (Gill.) 



IDIACANTHUS, Peters. 



Idiacanlhus, Peters, Monatsber. Acad. Wiss. Berlin, 1876, 846. — GCnther (type, J.fasciola, Peters), Chal- 

 lenger Report, xxn, 215. 

 Baihyophis, Guntiier, Ann. and Mag. Nat. Hist., 1878, 5th series, II, 181. 



Body extremely narrow and elongate, snake-like, naked. Vent far behind the middle 

 of the length of the body. Head large, compressed, with the snout of moderate length, and 

 with the cleft of the mouth nearly as long as the head. Teeth in the jaws extremely large, 

 numerous, of unequal size, depressible. Similar teeth on the tongue and on each side of 

 the vomer. Eye rather small. Opercular portion of the head narrow. A long barbel 

 anteriorly on the hyoid. The dorsal commences above the ventrals, and extends nearly 

 to the anal ; the anal also is long, commencing behind the vent. Pectorals none. Ventrals 

 inserted before the middle of the body. A small phosphorescent organ above the mid- 

 dle of the upper jaw, and a series of small, luminous dots along each side of the abdomen 

 and along the outer ventral ray. Similar organs on the tail. Gill openings extremely 

 wide. (GUnther.) 



Idiacanthus fasciola, the type of the genus. Mas described from two small surface 

 specimens in the Berlin Museum, from the seas north of New Guinea and Australia. 



