392 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



of these authors indicate that they have had another species, in which 

 the interorbital is nearly as wide as the orbit. In addition Vaillant 

 counted 9 ventral rays ("I, 8") and Collett 7+27 gill-rakers on the 

 outer arch, while G. longifilis has but 8 ventral rays, and 30 to 35 

 gill-rakers below the angle of the outer arch. Alcock's, 1 Brauer's 2 

 and Weber's 3 records of this species from the Indian Ocean and East 

 Indian Islands seem to be all erroneous. The species of these authors 

 are distinguished from the true longifilis by their wider interorbital 

 space and more numerous pyloric caeca. 



The number of pyloric caeca in the species of Gadomus*, with the number of 



specimens counted. 



G. longifilis (Goode and Bean) S (one). 



G. sp. (Hawaiian Islands) 5 12 (one). 



G. melanopterus 15 (one). 



<!. multifilis (Philippine Islands) 12 (one). 



G. multifilis (Japan) 16 (one). 



" Bathygadus longifilis " of Al cock 20 (one?) 



" Bathygadus longifiUs" of Braner 15 to 22 (two). 



G. magnifiUs 24 to 29 (two) 



G. introniger 35 to 52 (several). 



G. denticulatus 61 to 75 (three). 



G. colletti _* 95 (one). 



The number of pyloric caeca occurring in the different species of 

 Gadomus thus form a very striking series, in which the number 

 gradually becomes smaller as one passes from the species with the 

 firmest, narrowest heads and the fewest gill-rakers, to those of the 

 more bathybial types, with contrasting characters. 



ANALYTICAL KEY TO THE SPECIES OF GADOMUS. 



a\ Fins without long filaments; pectoral broad, with 25 rays; teeth excessively 

 minute; interorbital much narrower than orbit. 



areuatus (western Atlantic). 

 <r. Fins with long filamentous rays ; pectoral narrower, with 15 to 22 rays. 



b\ Gill-rakers on lower limb of outer arch, 17 to 25, blunt at their tips 

 (undescribed in G. dispar, a species not closely related to those of 

 groups b' 2 and b 3 ). 



c\ Interorbital 2 in "eye" dispar (Eastern Atlantic). 



c 2 : Interorbital 1.57 to l.S in orbit ; gill-cavity with a whitish band on 



opercular margin ; gular membrane light brown. 



d x . Teeth so excessively minute and crowded as to form an even 



shagreen-like surface, on which the individual teeth cannot be 



distinguished by the unaided eye; filamentous rays shorter, the 



dorsal spine less than twice as long as head ; pyloric caeca 61 



to 95. 



e\ Band of teeth in upper jaw little expanded posteriorly, its greatest 



width half that of bony suborbital region; color lighter; head 



firmer; pyloric caeca 95 colletti (Japan). 



1 Alcock, Ann. Mag. Nat. Hist, ser. 6, vol. 6, 1890, p. 302 ; and ser. 6, vol. 8, 1891, p. 

 123; Desc. Cat. Indian Deep-Sea Fishes, 1899, p. 120. 

 - Brauer, Die Tiefsee-fische, 1906, p. 270, pi. 12, fig. 7. 



3 Weber, Die Fische der Stbofira-Expedition, 1913, p. 172. 



4 All of the counts were made by us, excepting those credited to Alcock and Brauer. 

 6 Gilbert, Bull. U. S. Fish Comm., 1903 (1905), sec. 2, p. 659. 



