282 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 



loric cceca few. Dorsal fiu near the middle of the body; ventrals 

 usually below it, with 8 rays 5 pectorals well developed; adipose fin 

 small ; aual usually long. Small fishes of the opeu seas in most re- 

 gious; species numerous. Several undescribed species have been lately 

 taken off our Atlantic coast by the U. S. Fish Commission, (i^ul, night; 

 9?"?, light; hence amended by Cocco to Nyctophus.) 



466. M. CB'eEBtllarc Jordan & Gilbert. 



Body much compressed, deepest in front of the base of the pectorals, 

 bluntly convex anteriorly, tapering behind. Ventral region much more 

 arched than dorsal. Caudal peduncle long and very slender. Head 

 short and high, abruptly rounded in profile, the snout very blunt. 

 Jaws equal, the snout not projecting beyond the mouth. Maxillary 

 very slender, scarcely widened to its tip, and not dilated, its extremity 

 reachiug beyond the eye to the margin of the preopercle. Preniaxilla- 

 ries anteriorly on a level of the pupil. Teeth very small, present on 

 all the dentigerous bones. Eami of the mandible nearly parallel, com- 

 ing together in a sharp keel below. Orbital margin above and in front 

 with a thin membranaceous rim, that in front distiu(«t and formed by 

 the upturned edge of the preorbital. No orbital spine. Nasal bones 

 membranaceous, their edges upturned, forming a horizontal groove. 

 A groove between the frontal bones. Orbital margins separated by 

 a groove from the preopercle. Margin of preopercle very oblique. 

 All the membrane bones extremely thin, papery. Eye large, 3^ in 

 head. Gill-rakers long and slender. Head 3| in length to base of 

 caudal ; depth 4J. Head and body completely covered with thin mem- 

 branaceous scales, those on the middle of the sides not elevated and 

 not noticeably larger than the others. Free edges of all the scales 

 crenulate, some of them, especiallj- on the back, with the crenations 

 acute, but without spines, the scales being truly cycloid. About 45 

 scales in a longitudinal series. A phosphorescent spot on each man- 

 dible near the symphysis, 33 pairs of spots along the bell}', G in front 

 of ventrals, 6 between ventrals and origin of anal, and 21 between 

 front of anal and base of caudal. Caudal peduncle above and below 

 with two or three backward-directed spines, which are apparently the 

 exserted tips of vertebral processes. D. 12; A. 10; the fins rather 

 low. Origin of dorsal nearer the snout than the base of caudal, much 

 behind the base of the ventrals. Ventrals short, not reachiug half way 

 to vent. Pectorals reaching base of ventrals. Color very dark steel- 

 blue above, silvery on sides and below, with dark metallic lustre; the 



