380 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



e\ Gill-rakers 6+17 ; eye half length of snout or of interorbital 



space cottoides. 



e 2 . Gill-rakers 5 or 6+19 to 22 ; eye more than half length of snout 



or of interorbital space spotigiceps. 



d 2 . Insertion of ventral fins below that of pectorals ; distance from 

 anus to base of ventral equal to the postorbital length of the head ; 



color light favosus. 



b*. First dorsal, pectoral and ventral fins each with a filamentous ray 

 longer than the head; color lighter than in B. boircrsi or B. cot- 

 toides antrodes. 



a 2 . Orbit more than two-thirds interorbital width (orbit 1.4 to 1.6 in inter- 

 orbital in B. filamcntosus) ; head only moderately wide and cavernous; 



scales on mandible in li or 2 series (melanobranchus). 



f\ First dorsal, pectoral and ventral fins each with a filamentous 



ray longer than the head. 



f/\ Barbel not present ; orbit 1.4 to 1.6 in interorbital width ; 



about 20 gill-rakers on lower limb of outer arch-filamoitosus. 



<f. Barbel small, but evident; orbit 1.0 in interorbital width; 35 



gill-rakers on lower limb of outer arch micronema. 



f. Fins without long filaments. 

 h 1 . Barbel absent. 



i\ Ventral with 10 rays ; 19 gill-rakers on lower limb of outer 

 arch ; pseudobranchiae present ; interorbital little wider 

 than orbjt, 3.7 in head ; snout scarcely longer than orbit ; 



branchial cavity wholly black entomelas. 



f. Ventral with 8 or 9 rays. 

 f. Orbit shorter than snout. 



fc\ 19 to 21 gill-rakers on lower limb of outer arch ; 

 pseudobranchiae present in adult ; interorbital 4 in 



head ; branchial cavity wholly black furvesccns. 



k 2 . 16 gill-rakers on lower limb of outer arch ; pseudo- 

 branchiae absent in adult ; interorbital 3.43 in head ; 

 colcr much lighter, the posterior margins of the 

 opercular and gill membranes irregularly lighter or 



whitish - nipponicus. 



f. Orbit decidedly longer than snout, about equal to inter- 

 orbital width melanobranchus. 



h*. A small barbel present. 



1 1 . Interorbital wider than eye garretti. 



1 2 . Interorbital much narrower than eye. 



m\ Inner shagreen-like portion of premaxillary band 

 of teeth forming only a narrow border to the 

 band ; orbit 4 in head ; ground color chocolate ; 

 iris dark; ventrals with 9 rays; barbel tuber- 

 cular sulcatus. 



m 2 . Inner shagreen-like portion of premaxillary band 

 of teeth about half as wide as the entire band ; 

 orbit very large, 2f to 3 in head ; ground color 

 silvery or gray, including iris ; ventrals with S 

 rays; barbel slender macrops 1 



1 Among the species of Bathygadus, B. vuicrops most closely approaches the genus 

 Qadomus as defined by us. 



