DISCUSSION OP SPECIES AND THEIR UISTRIIJUTIuN. 129 



IDIACANTHUS PEKOX, Gunther. (Figure 151.) 



Balhyophw feror, Gunther, Ann. and Mag. Nat. Hist. 1878, ii, 181. 

 Idiaeanthus ferox, Gunther, Challrni^er Keport, xxii, 216, jil. lii, fig. V. 



Vent situated at tlie sixth cisiith of the total length. Oommencemcnt of the doreal fin 

 opposite to the root of the ventrals. Black. D. (50; A. -iS; V. 6. ((lunther.) 



The VhaUenger obtained one specimeD, 8 inches long, at station G3, in the middle of the 

 North Atlantic; depth, 2,750 fathoms. 



Order LYOPOMI. 



Lyopomi, Gill, American Naturalist, 1889 (Nov.), 1010. 



Teleosts with the scapular arch constituted by the proscapuln, ]iostero-teniporal and 

 post-temporal, the post-tempornl discrete from the side of the craiiiuin, and impinging on 

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

 men in the upiier margin of tlie hypocoracoid; the me.socoracoid absent; the actinosts 

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

 ratus characteri.stic, 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 pieoperculnm, in com- 

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

 jawbones complete and normal; palatines, entopterygoid, and ectopterygoid normally de- 

 veloiicd; the anterior vertebras separate, and the ventrals abdominal. 



Family HALOSAURID^^. 



Baloaaiiridw, GOnther, Cat. Fisli. Brit. Mus., vir. IStiS, 4S2. 



Body covered witli 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 in moderate number. Pseudobrauchiie none; air bladder large, simple; giU 

 openings wide. Ovaries closed. 



KEY TO THE GENERA AND SPECIES OF HALOSAURIDJi. 



I. Ventrals normal. No second dorsal lin. 



A. Vertex covered with scales. Scales of latorallino scarcely enlarged. Snout obtusely rouuded. Head 



vrithout angular ridges. Anal comparatively high Hai.osauru.s 



1. Preoral portion of snout equsil to half its length. 



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

 of eye two-fifths postorliital portion of head and much greater than width of interorbital 

 space. About 60 scales in later;il line in front of vent H. OwEXii, Johnson 



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



Height of body about one-third length of head 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 Literal line in front of vent H. Johnsoxianis. Vaillaut 



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

 and much greater tlian width of intcrorliital space. About (57 scales in lateral line in front 

 of vent tl- GC'NTHERi, Goode and Beau 



B. Vertex scaleless. Scales of lateral line enlarged, provided with photophores. Snout pointed. Head 



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



that of dorsal Aldrovandia, Goode and Beau 



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



a. Preoral portion of snout exceeds half its length. Diameter of eye considerably less than width 

 of interorbital space. Twenty-four scales in Lateral line in front of vent. 



A. Rd.sTKATA (Giiuther) 



19868— No. 2 9 



