FISHERY BULLETIN: VOL. 72. NO. 2 



regions. Dendritic, deep pigmentation at base of 

 dorsal fin on myotomes 14-20 and 50-57, and on 

 anal fin on myotomes 32-51. 



Remarks: This species differs from all the 

 three species ofMonognathus described by Bertin 

 (1938) and from M. jesse described in this 

 account in having a high myotome count of 113. 

 The structure of the caudal fin also is different. 

 In M. bruuni and M. jesperseni the urostyle is 

 produced into a needlelike structure forming a 

 false caudal fin along with the dorsal and anal 

 fin rays. In M. taningi the urostyle is produced 

 into a very long, whiplike structure. The urostyle 

 in this species is spinelike, surrounded by a large 

 paddle-shaped, compressed structure. The eth- 

 moid tooth is small and does not project into the 

 mouth. If Bertin's ( 1938) observations are correct, 

 this species differs from the above three species 

 also in having four gills as only one gill was 

 figured in his drawings. There is a series of three 

 closely packed teeth at the tip of the lower jaw, 

 and such a series is not seen in the forms described 

 by Bertin. 



curved, tip armed by 5 closely packed large teeth 

 followed by 11 teeth of characteristic shape. No 

 opercular bones or branchiostegals recognizable. 

 Gills four, small, but proportionally larger than 

 those of M. ahlstromi. First gill slit smallest, 

 second and third largest, last gill slit slightly 

 larger than first. Gill filaments short and folia- 

 ceous, alternately on either side. First three gills 

 holobranchs, fourth a hemibranch. All gills 

 covered by membranous operculum. Gill opening 

 vertical, moderate in size, in front of pectoral 

 fin. Myotomes W-shaped, 26 -h 78 = 104. 

 Vertebrae heavy, shorter in length in trunk 

 region, slender and elongate in tail region. 

 Esophagus short with opaque girdlelike region. 

 Stomach voluminous, recurved at end. Intestine 

 a straight tube, shorter than stomach, situated on 

 right side of stomach. Liver lobular. Pancreas and 

 heart lost due to damage. Dorsal fin originates 

 on myotome 11, relatively high, with 80 unseg- 

 mented rays. Anal fin originates on myotome 30, 

 with 54 unsegmented rays. Urostyle depressed, 

 lanceolate, with middorsal ridge. Pectoral fin 

 small, triangular, rays indistinct. 



MONOGNATHUS JESSE SP. N. 



Figures IF; 2F-N 



Holotype: SIO 60-245, central North Pacific, 

 12^07. l'N-12^23.8'N, 148^35. l'W-148=18.0'W, 

 0-2,100 m, IKMT, 1(63 mm), 9-10 July 1960. 



Description: Body compressed except at head. 

 Preanal region deep due to voluminous stomach, 

 preanal region 3.9 in total length. Postanal region 

 3.6 in total length, tapering to point. Body covered 

 with loose semitransparent skin. Maximum depth 

 at middle of preanal region, 12.6 in total length. 

 Head deep, large, 8.7 in total length. Snout blunt, 

 membranous, small, 4.7 in head. Olfactory organ a 

 slightly curved short tube, open at both ends. 

 Eye rudimentary, 11.2 in head, oval, lens 

 extremely small. Gape of mouth reaching beyond 

 eye. Upper jaw degenerate, membranous, unsuit- 

 able to serve as jaw, no maxilla recognizable, no 

 teeth. Median ethmoid tooth large, pointed, tip 

 calcified and bifid, surrounded and hidden by soft 

 tissue. Ethmoid glands paired oval bodies, one 

 on either side of tooth. Lower jaw long, slightly 



Pigmentation: Brown chromatophores on 

 snout, tip of lower jaw, at angle of mouth. 

 Dendritic brown chromatophores on head, pre- 

 dorsal region, gill membrane, lateral side of body 

 as far back as anal region. Three deeply seated 

 melanophore patches (seen only if cleared in 

 glycerine) at base of dorsal fin inside myotomes, 

 one long patch on myotomes 5-22, second on myo- 

 tomes 40-43, and third on myotomes 58-62. Anal 

 fin has similar large patch on myotomes 30-39. 



Remarks: This species differs basically from 

 the three species described by Bertin (1938) and 

 from M. ahlstromi in the presence of a small 

 pectoral fin, structure of the urostyle, myotome 

 number, dentition of the lower jaw, relatively 

 longer tail, and fin ray counts. Bertin (1938) 

 gave no account of the pigmentation of his speci- 

 mens, hence it is not possible to compare pig- 

 mentation. The pigmentation in this specimen 

 differs from that of M. ahlstromi in the follow- 

 ing respects. There is additional pigmentation 

 on the head, angle of the lower jaw, and gill mem- 

 brane, more profuse pigmentation on the lateral 

 side of the body and predorsal region, and three 

 patches at the base of the dorsal fin. 



552 



