DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 497 



structure. Tlio basal portiou of the cephalic appendage is about twice as long as the very- 

 small eye. The maxillary is a very slender, narrow bone, extending about as far backward 

 as the intermaxillary. The intermaxillary is slightly protractile and has about 10 teeth 

 ou each side, several of which are nearly twice as large as the rest; its length is two-fifths 

 of the total without caudal. The mandible is as long as the head without the snout; it has 

 .S teeth on each side, the anterior i)air and several other pairs along the shaft of the 

 bone being greatly enlarged. A pair of enlarged teeth on the head of the vomer; several 

 similar teeth on the palatines. Upper pharyngeals armed with several strong teeth. The 

 eye very small, inconspicuous ; its distance from the tip of the snout equals nearly one-third 

 its distance from the origin of the soft dorsal. Intestine shorter than length without caudal. 



The soft dorsal has IG rays, all of which, except the last four, are greatly produced; 

 the second, tliird, and fourtli rays, are the longest; they are nearly twice as long as the 

 body. The anal consists of l-l rays, all of which, except the last three, are much produced. 

 The fin is not quite perfect, yet its anterior rays are longer than the body. The caudal 

 contains 8 rays, of which the four inner ones are divided, while the rest are simple. The 

 middle rays are as long as the distance from the tip of the lower jaw to the base of the 

 pectoral. The pectoral is comparatively short and contain s 16 simple articulated rays, 

 the longest of which is about one-half as long as the head. 



About 9 luminous filaments on each side of the head, 7 more between the nape and 

 the dorsal, and about 12 on the sides. The filaments are nearly twice as long as the eye. 



Head and body black ; caudal cephalic tuft, and most of the fin-rays pale. 



The type of the species is number 39265, taken by the steamer Albatross, September 

 19, 1887, in N. lat. 39° 27', W. Ion. 71° 15', 1276 fathoms. 



Family ONCHOCEPHALID^E. 



MdUha'oidci, GiLL, Trnc. Acad. Nat. Sci. Phila., 1863, 89 (diagnosis). 



Mallhwoidw, Gill, Arrangemoiit Families of Fishes, 1872, 2 (No. 10); Proc. U. S. N. M., I, 1878, 215-219 (diag- 



nosis) p. 231 (key to subfamilies and genera); v, 1883, 555 (with elaborate synonymy). 

 Malthida;, Jordan and Gilbert, Bull. 16, U. S. Nat. Mus.. 849 (diagnosis and key). 

 OnckocepMlidcv, Gill, MS. 



Tediculates with very broad and depressed head, with snout more or less elevated, 

 with trunk short and slender. JNIouth not large, subterminal or inferior, the lower jaw 

 included; teeth villiform or cardiform. Gill openings very small above and behind the 

 axils of the pectoral fins. Body and head covered with bony tubercles or spines. Spinous 

 dorsal reduced to a small rostral tentacle, which is retractile into a cavity under a promi- 

 nent process on forehead; in one genus the rostral tentacle is obsolete; soft dorsal and anal 

 small and short; ventrals well developed; pectoral well developed, its base strongly angled, 

 with long pseudobrachia and 3 actinosts. Branchiostegals 5; no i)seudobrauchiie. 



KEY TO THE SUBFAMILIES AND 6ENEEA. 



I. Body with disk cordiform .and caudal portion stout. 



A. Frontal region elevated, and snout more or less produced or .attenuated forwards OnchocephaVinw 



1. Orbits lateral, teeth ou vomer and palatines. 



0. (iills 2i ONCirOCEPHALUS 



h. Gills 2 Malthopsis (See Appendix.) 



II. Body with disk subcinular or expanded backwards and caudal portiou slender; froutiil region depressed, 

 and snout rounded and obtuse in front Halieutaina; 



A. Palato edentulous; rostral tentacle develoi)ed; carpus exserted from common membrane. 



1. Disk subcinular; gills 2i pairs. 



a. Mouth cleft wide, subvertical. Prickles strong HaLIEUTJEA 



ft. Mouth small, terminal. Prickles feeble Halieutella 



2. Disk subtriaugular; mouth small; gills 2 pairs DlBRANxnus 



B. Palate deutigerous; dorsal (in obsolete; rostral tentacle present H.vlicmetus 



C. Palate and vomer dcutigcrous ; dorsal present ; no rostral tentacle HAtiEUTICHTHYS 



11)868— No. 2 32 



