gilbert: the lantern-fishes of japan 85 



Genus Diaphus Eigenmann & Eigenmann. 



Key to Japanese Species of Diaphus. 



a. Pre-orbital photophore confined to a single minute dot above the nostril. 



h. Upper supra-anal and the posterolateral immediately below the lateral line. . D. agassizi. 



66. Upper supra-anal and the posterolateral far below the lateral line D. nipponensis. 



aa. Upper pre-orbitals on the front of the snout, directed forwards hke headlights, occupying each a 

 roundish depression above the nostril, 

 c. Accessory gland developed in connection with suprapectoral only. 



d. Lower pre-orbital widely separated from the upper on lower anterior border of 

 orbit, a minute detached subocular point usually present behind it. Pre- 



opercular border nearly vertical D. nanus. 



(M. No lower detached pre-orbital, the upper continuous with a narrow strand along 

 anterior border of orbit. Pre-opercular border oblique. 

 e. Third ventral elevated, in line with supraventral, second supra-anal and 

 first antero-anal. Third precaudal midway between first and fourth, 



the last interspace much the widest D. tanakae. 



ee. Third ventral low, much below the line joining supraventral and second 

 supra-anal. Last precaudal interspace little wider than the others. 



D. sagamiensis. 

 cc. Accessory glands developed in connection with all the photophores of the upper lateral 



series. No lower pre-orbital, a large suborbital D. glandulif er. 



aaa. A narrow luminous bar on upper and one on lower orbital border, the latter continued as a very 



narrow strand around front of orbit D. anteorbitalis. 



aaaa. Pre-orbital expanded to cover the entire snout D- gigas. 



aaaaa. Pre-orbital not as above, narrow, occupying the anterior or anterior and inferior border of the orbit, 

 without detached portion (the upper portion expanded above nostrils in D. sagamiensis). 



f. Upper series of photophores well below the lateral line D. coeruleus. 



ff. Upper series of photophores immediately below the lateral line. 



g. Pre-orbital not continued along lower margin of orbit. First antero-anal greatly 



elevated, nearly vertically above the second D- latus. 



gg. Pre-orbital continuous with a luminous strand which extends along the most of 

 the inferior border of the orbit. First antero-anal not greatly elevated, above and 

 anterior to the second D. sagamiensis. 



14. Diaphus agassizi Gilbert. 

 Diaphus agassizii Gilbert, Mem. Mus. Comp. ZooL, XXVI, 1908, p. 226, Pi. 2 



(Marquesas Islands). 



Several specimens, the largest 26 mm. long, from Suruga Bay, in open 

 intermediate net at 300 fathoms. 



In the figure of the type above cited, the suprapectoral should be higher, 

 a little above the level of the supraventral, and somewhat nearer lateral line 

 than base of pectoral. Also, the third ventral should be higher on side, on a 



