DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 129 



IDIACANTHUS FEROX, Gunther. (Figure 151.) 



Untln/nphiKferor, GiiNTHER, Ann. anil Mag. Nat. Hist. 1S78, ii, 181. 

 IdiacanthiiK fcrox, GOnther, Challenger Report, XXII, 216, pi. LII, fig. 1). 



Vent situated at the sixth eighth of the total length. Commencement of the dorsal fin 

 opposite to the root of the ventrals. Black. D. 60; A. 45; V. 6. {Gihither.) 



The Challenger obtained one specimen, 8 inches long, at station 63, in the middle of the 

 , North Atlantic; depth, 2,750 fathoms. 



Order LYOPOMI. 



Lyopomi, Gill, American Naturalist, 1889 (Nov.), J016. 



Teleosts with the scapular arch constituted by the proscapula, postero-temporal and 

 post-temporal, the po.st-temporal discrete from the side of the cranium, and impinging on 

 the supra occipital; the hypercoracoid and hypocoracoid lamellar, and the fenestra or fora- 

 men in the upper margin of the hypocoracoid; the mesocoracoid absent; the actinosts 

 normal; the cranium with the condyle confined to the basi-occipital; the opercular appa- 

 ratus characteristic, the preoperculum being entirely detached from the suspensorium, rudi- 

 mentary, and connected only with the lower jaw; the operculum normally connected; the 

 suboperculum enlarged and partly usurping the usual position of the preoperculum, in com- 

 pany with the suborbital chain, which is extended backwards toward the opercular margin ; 

 jaw bones complete and normal ; palatines, entopterygoid, and ectopterygoid normally de- 

 veloped ; the anterior vertebrae separate, and the ventrals abdominal. 



Family HALOSAURID.^. 



Hahsaurida; GItnther, Cat. Fish. Brit. Mus., vii, 1868, 482. 



Body covered with cycloid scales; head scaly; barbels none. Margin of the upper jaw 

 formed by the intermaxillaries mesially, and by the maxillaries laterally. Opercular appa- 

 ratus incomplete. Adipose fin none. The short dorsal belongs to the abdominal part of 

 the vertebral column; anal very long. Stomach with a blind sac; intestine short; pyloric 

 appendages iu moderate number. Pseudobranchiie none; air bladder large, simple; giU 

 openings wide. Ovaries closed. 



KEY TO THE GENERA AND SPECIES OF HALOSAURID^. 



I. Ventrals uorm.al. No second dorsal fin. 



A. Vertex covered with scales. Scales of lateralline scarcely enlarged. Snout obtusely rounded. Head 

 without angular ridges. Anal comparatively high Halgsaurus 



1. Preoral portiop of snout equal to half its length. 



Height of body nearly equal to half length of head and one-seventeenth of total. Diameter 

 of eye two-fifths po.storbital portion of head and much greater than width of interorbital 

 sjiace. About 60 scales iu lateral line in fnmt of vent H. Owenii. Johnson 



2. Preoral portion of snout less than half its length. 



Height of body about oue-third length of h(>ad and one twenty-fifth of total. 

 Diameter of eye nearly two-fifths of postorbital portion of head and equal to width of inter- 

 orbital space. About 55 scales in lateral line in front of vent .. ..H. JonN.soNlANUS, A'aillant 

 Diameter of eye half length of postorbital portion of head (which is equal to that of snout), 

 and much greater than width of interorbital space. About 67 scales iu lateral line in front 



of vent H. Gt'NTHERi, Goode and Bean 



1?. Vertex sealeless. Scales of lateral liue enlarged, provided with jihotophores. Snout pointed. Head 

 with prominent lateral ridges. Anal moderately high, its height one-third to one-fourth of 



that of dorsal Aldrovanma, Goode and Beau 



1. Suout much produced (length equal to or greater than distance from eye to root of pectoral). 



a. Preoral portion of snout exceeds half its lingth. Diameterof eye considerably lessthan width 

 of interorbital space,. Twenty-four scales in lateral line iu front of veut. 



A. ROSTKATA (GUnther) 

 19868— No. 2 9 



