Jordan and Evermann.— Fishes of North America. 2079 



lary none on lower jaw, the mucous pores bordered by lobed flaps. Gill 

 membranes broadly united, joined t.. isthmus, without fre.- fold. Dorsal 

 fins well separated; anal beginning about 3 plates in front of beginniug 

 of second dorsal; pectorals 5§ in body, their base 3i in their length, with 

 1-, or 16 oraduated rays, the uppermost longest; ventrals of male nearly 3 

 in head.^about equal to long diameter of orbit, those of female f to % as 

 long as those of male ; caudal about 3 times as long as wide at base. Lat- 

 eral line with 43 or 44 pores; plates spineless, rather large. In a youOg 

 male 2 inches long the median rostral plate is absent, all the plates on 

 breast sharply ridged and spinous; vent near tip of ventrals, \ of the dis- 

 tance from A'tM.trals to anal, with 5 pairs of minute spinous plates between 

 ventrals and vent. Body not tapering uniformly; broader in front, nar- 

 rowin- abruptly near front of first dorsal; tail not so much depressed; 

 head 3i in body length. Color light above, blue black on under side of 

 head; breast and belly dusky; all the fins intensely blue black. Pacific; 

 known from the Aleutian Islands, Bering Sea, south to coast of Washing- 

 ton; abundant in 350 to 477 fathoms. Here described from Dr. Gilbert's 

 types. Dr. Gilbert observes: 



In adult specimens the lower pectoral rays show .a tendency to elongate, as in XenocU- 

 rus but the fin is never distinctly notched. The k.vver.iaw always strongly protrudes, 

 and the genus difiers further in the very thin cranial bones and the inordmate develop- 

 ment of the raucous system. In addition to the specific characters mentioned m the 

 original description, we note that the eyeball does not exhibit the usual row of prickles 

 aulthat 2 barbels are usually present at end of maxillary, either black or white in color^ 

 The majority of che specimens were obtained north of Unalaska Island, but it was a lo 

 taken south of the Islands, and off the coast of Washington, at Albatross Stations 3210, 

 3316, 3324, 3325, 3329, 3330, 3331, 3337, and 3343 ; depths 109 to 483 fathoms. 



(niger, black; innna, fin.) 

 Bathyagonus rdgrwinnis, Gilbert, Proc.U. S.Nat. Mus. 1890, 89, Aleutian Islands and 

 coast of Washington. (Coll. Albatross.) 



774. XENOCHIRUS, Gilbert. 

 Xenochiriis, Gilbert, Proc. V. S. Nat. Mus. xiii, 1890, 90 (triacanthus) . 



Spinous dorsal present. Jaws equal or the upper the longer. Plates of 

 body spinous. Gill membranes united to isthmus, the posterior edge 

 sometimes forming a very narrow free fold across throat. Tip of snout 

 with a movable median plate or spine. Teeth well developed on ,iaws, 

 vomer, and palatines. Pectorals divided by a deep notch into 2 portions, 

 the lower comp..sed of greatly thickened rays which are simple and tre- 

 quentlv longer than those of the upper lobe, these lengthened rays not 

 usually developed in the young. A series of small spines on eyeball above 

 pupil North Pacific. This genus is very close to Bathyagonus which 

 represents it in deeper water. Both are near Odonioprjxis, but the relation 

 to Averruncus and Sarritor is more remote, aevoi, strange ; x^ip, l^and. ) 



a. Rostral plate with 3 upright spines. pentacanthus, 2423. 



6. Breast with numerous plates. at ascanus ''4'4 



Breast smooth ; plates of body rougher. ALASCAnus, -4-4. 



aa. Rostral plate with 1 upright spine. vtifrons '>425 



c. Gill membrane with posterior free fold triac v™ 4''6 



cc. Gill membrane without posterior free fold. triacanthls,, .4.d. 



