186 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



NORTHERN SPECIMENS. 



A Ibatrnss station 



Total length, mm 



Length to anvs, mm 



Length, head 



Length, orbit 



Width, interorbital 



Width, suborbital 



Orbit to preopercle 



Length, snout 



Length , maxillary 



Length, barbel 



Depth , body 



Width, body 



Anus to ana"l 



Anus to ventral 



Ventral to isthmus 



Height, second dorsal spine. . 



Height, third dorsal ray 



Length, first dorsal base 



Interdorsal space 



Length, pectoral fin 



Length , first pectoral ray . . . . 

 Length, second pectoral ray. 

 Length, third pectoral ray.. . 

 Length, outer ventral ray.... 

 Length, second ventral ray. . 



Soft rays, first dorsal 



Ventral rays 



Pectoral rays 



5049 

 385 

 100 

 76 

 23 

 24 



9 

 34 

 26 

 28.5 



4 



52 

 29 

 12 

 20 

 20 



5049 

 355 



25 



9 

 33 

 26 

 27 



3.5 

 50 

 33 



n 



18 



27.5 



39 



17 

 35 



44.5 



17 

 34 

 42.5 



5048 

 134 



Genus HYMENOCEPHALUS Giglioli. 



This genus is the most distinct of any in the subfamily. It is dis- 

 tinguished from all other Macrouroid fishes, with the exception of 

 Stelnd.achneiia argentea, by the presence of ventral striae, consisting 

 of fine parallel lines of dark, alternating with silvery, pigment, on 

 the ventral areas of the body. There are invariably two " lens-shaped 

 bodies," possibly photophores, on the mid-ventral line, one immedi- 

 ately before the anus and one before the ventrals, connected by a 

 black ridge along the wall of the abdominal cavity. The large thin 

 scales with weak spiniiles, the papery structure of the bones of the 

 head, and the narrow pectoral are characteristic of HyTnenocejjhalus, 

 In several characters, Hyraenocephalus resembles Bathygadus and 

 its allies. Among these may be mentioned the large modified scales 

 over the sensory canal on the side of the head, anterior to the origin 

 of the lateral line; the large sensory canals; the anteroventral exten- 

 sion of the gill opening ; the comparatively wide slit before the first 

 arch ; the numerous gill-rakers (more than 15 on the lower limb of the 

 outer arch) ; the large lateral and subterminal mouth; the thin scales; 

 the variation in the barbel, which is absent, rudimentary, or well 

 developed in diiferent species within each group. It resembles the 

 Bathygadus group also in having seven branchiostegals, correlated 

 with a posterior position of the anus, which is immediately before 

 the anal fin. 



The 13 known species are all fragile and small, less than 1 foot in 

 length, and are confined entirely to tropical or subtropical waters. 



