Jordan and Everfnann. — Fishes of JVorth America. G05 



291. IDIACANTHUS, Peters. 



Idiacanlhiis, I'eteus, Moiiatsber. Akad. Wiss. Berlin, 1876, 846, {fasciola). 

 Bathyophls, GOntiier, Ann. Mag. Nat. Hist., 1878, 181, (fernj:). 



Body suake-like, very slender and elongate, scaleless. Vent very far 

 back. Head large, compressed, the snout moderate, the cleft as long as 

 head. Teeth extremely large, numerous, unequal, fang-like, depressible, 

 present on jaws, vomer, and palatines. Eye small ; opercles narrow. 

 Hyoid bone with a long barbel. Dorsal long and very low, extending 

 from above ventrals nearly to caudal ; the rays simple, each one placed 

 behind a pair of spine-like processes ; no adipose fin ; no pectorals; ven- 

 trals median. A luminous organ above middle of upper jaw and a series 

 of luminous dots along side of belly and on outer ray of ventral and on 

 tail. Gill openings very wide; bvanchiostegals short, numerous. Gills 

 4; no pseudobranchite. Y ertohr se. nnmerons, 67 in Idiacunthus J'er ox. Three 

 species known. (ttS^of, peculiar ; «/cav^a, spine.) 



a. Dorsal fin inserted opposite root of ventrals; anal rays 45. ferox, 903. 



aa. Dorsal fin inserted well in advance of ventrals; anal rays about 35. antrcstomus, 904. 



903. IDIACANTHUS FEROX (Giinther). 



D. 60; A. 45; V. 6. Vertebraj 67. Vent in sixth eighth of total length. 

 Dorsal inserted opposite ventrals. Color black. North Atlantic, nearly 

 midway, in 2,750 fathoms. One specimen, 8 inches long. (Giinther.) 

 (ferox, fierce.) 



Bath i/oph in ferox, Gt'NTHER, Ann. Mag. Nat. Hist., ir, 1878, 181, North Atlantic. 

 Idiacanlhiis ferox, Gunther, Deep-Sea Fishes Challenger, xxii, 216, 1887. 



904. IDIACANTHUS ANTROSTOMUS, Gilbert. 



Head 12; depth 16. D. 57; A. about 35. Abdomen much dilated, 

 abruptly constricted immediately behind the ventral tins, and much nar- 

 rowed auteriorly, the depth again increasing to occiput. Greatest depth 

 Immediately in froiit of ventrals. Maxillary reaching edge of gill cover. 

 Teeth in a single series in each jaw, readily depressible, varying greatly 

 in length ; teeth in the upper jaw arranged in groups of 4 or 5, the 

 anterior member of each group being very short, the others rapidly 

 increasing backward, the posterior tooth very long ; lateral teeth in 

 mandible inserted at the extreme outer edge of the jaw, the anterior teeth 

 inserted farther inward; thus the last of the anterior teeth are distinctly 

 within the first of those on sides of jaw ; a single small tooth on each 

 side of vomer, and 2 or 3 posteriorly on palatines ; 3 pairs of teeth 

 directed backward from near tip of tongue. Eye over first third of 

 length of maxillary ; lower jaw much longer than the upper. Barbel J 

 longer than the head, expanded near its tip, and again narrowed as in /. 

 ferox. Dorsal beginning well in advance of ventrals, its distance from 

 tip of snout 3^ in total length ; anterior rays distant, the membrane 

 from one ray reaching only to basal portion of the succeeding ray ; each 

 ray starting behind a pair of short spinous projections which diverge back- 

 ward, the fin when depressed lying in the groove formed by these diverg- 

 ing pairs of spines ; caudal forked, the rudimentary rays extending well 



