162 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



Nostrils elongate, the exterior slit occupying the middle third of the space between the an- 

 terior margin of the orbit and the tip of the snout. Length of the neck four-fifths that of 

 the head, equal to the distance from the posterior limit of the nostril to the posterior por- 

 tion of the head. Pectorals ins(!rted high up, almost in median line, and composed of two 

 or three flexible, filiform rays. Origin of the dorsal about midway between the vent and 

 the tij) of the snout, the fin composed of flexible, delicate rays, not sufflcieutly differentiated 

 from the thin membrane as to be easily counted, those rays being longest in the region above 

 the vent. 



Vent nearly median. Anal flu beginning immediately behind the vent, and similar in 

 height and appearance to the dorsal fin, which it apparently joins at the tip of the tail. 

 No ventrals. 



Lateral line inconspicuoirs, with minute pores, though its location is emphasized by 

 the Amphioxus like arrangement of the muscular fibers. Length of type 8 inches ; of head, 

 one-half inch; of region in advance of pectorals, 1 inch; greatest height, seven-sixteenths 

 of an inch. Color, in life, ruddy brown ; in alcohol, light yellow. 



A single specimen (Cat. No. 33523, U. S. N. M.), was obtained by the Fish Commission 

 steamer Albafrons, from station 2094, in 39° W 30" N. lat., 71° 04' W. Ion., at a depth of 

 1,022 fathoms. 



Order HETEROMI. 



NotaoanOn, Bleeker, Tentameu, 1859, xxin (in part). 

 Heteromi, Gill, American Naturalist, Nov., 1889, 1016. 



Teleosts with the scapular arch formed by the proscapula and post temporal (or postero- 

 temporal), the latter detached from the sides of the cranium and impinging on the supraoc- 

 cipital; the hypercoracoid and hypocoracoid coalesced into a single lamellar imperforate 

 plate; the actinosts normal; the cranium with the condyle confined to the basioccipital 

 (ill-defined); the exoccipitals coalesced with the epiotics and opisthotics; the vomer 

 obsolete; the opercular apparatus complete, but the i)reoi)erculum slightly connected with or 

 discrete from the suspensorium ; the suborbitals suppressed; the jaw bones complete and 

 little aberrant; the palatines, entoptery golds, and ectopterygoids well developed; the 

 anterior vertebrae separate, and the ventrals abdominal. {Gill.) 



All the heteromous teleosts have a subfusiform, moderately compressed body with head 

 short and snout protruiling, sometimes produced, proboscis-like (as in Polyacanthonotus). 



Family NOTACANTHID^E. 



INofacantiiii, Eafinesque, Indice d' Ittiologia Siciliana, 1810, 34. 

 N'otacanthini, Boxaparte, Cat. Metodico, 1876, 72. 

 Notacanlhoidei, Bleeker, Tentamen, 1859, xxni. 

 Notacantki, GOnther, Cat. Fish. Brit. Mus., in, 1861, 544. 



Notacanthida, GiiJL, Arr. Fam.Fish, 1872, 21; Johnson's Cyclopedia, in, 1883; Century Dictionary, 4022.— 

 Jordan and Gilbert, Bull, xvi, U. S. Nat. Mus., 370. 



Mouth moderate, transverse, inferior. Lower jaw normal, with rami immovably con- 

 nected at symphysis. Scales small on body and head; lateral line present. Teeth slender, 

 closely set, in single series in each jaw. Gill openings wide, the membranes separate and 

 free from the isthmus. 



Dorsal fin median, with short and free dorsal spines, and with only one ray (if any) 

 behind. Anal fin long, rather high, extending from the middle of the body to the caudal, 

 with which it unites, and with numerous spinous rays. Ventrals abdominal, often con- 

 fluent,with 1-5 spines and 4-8 soft rays. Pectorals short and high up. Pseudobranchiai none. 



The elaborate anatomical description of Xotavantlim sexspinia, given by Giiuther (Chal- 

 lenger Report, XXII, 243-8) with numerous excellent figures, applies in its general features 

 to all the members of this family. In the discussion of the genera and species below, little 

 attention has been given to the degree of connection of the ventral fins. In every in- 



