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 (“1,8”) 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,! Brauer’s * 
and Weber’s * 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 /ongifilis 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. 
Giviongijilis s(Goodesands Bean) ess ee ee ae 8 (one). 
G. isp.) (la watlan 1s land $3) isso Sie ene oe 2 eee 12 (one). 
G.. MeELONO DLCTUS ESS ree SS SoS NG ee oo le aly (one). 
Ga Multi lis CEMA pies ES NANNG S)) ce ee eae et 12 (one). 
Ge ALG PULUS Ss CB Sp Baa) a sa a toe hae eye par pa 16 (one). 
<S BOthyoadus LONG lis Ot -AleCOC Ke see a eee eens eee 20 (one?) 
— BOChyOGdUs LONGLIS.2 Obibralere.= 2. eee ee 15 to 22 (two). 
EUG TU TUS, a a ae I Poet ee Ae Os ee ea 24 to 29 (two) 
Get NVETONUG CT 22 Re 2 EN a he Bee el ee eee a ae eee SOKO 52 (several). 
GitdentiGulatus = Se ee eee ey ee eee 61 to 75 ~=©(three). 
GSS COME EES at EE ee eae 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. 
arcuatus (western Atlantic). 
a, 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 0” and b*). 
Gara lay eitov anh erie Thole Creer te ee es dispar (Hastern Atlantic). 
c. Interorbital 1.57 to 1.8 in orbit; gill-cavity with a whitish band on 
opercular margin; gular membrane light brown. 
a. 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. 
ce’. Band of teeth in upper jaw little expanded posteriorly, its greatest 
width half that of bony suborbital region; color lighter; * head 
firmer: pyloric teVees Op ee ee 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, pl. 12, fig. 7. 
8 Weber, Die Fische der Siboga—Expedition, 1913, p. 172. 
* All of the counts were made by us, excepting those credited to Alcock and Brauer. 
5 Gilbert, Bull. U. S. Fish Comm., 1903 (1905), sec. 2, p. 659. 
