552 Bulletin ^7, United States National Museujn. 



Dorsal entirely in front of anal, and scarcely, or not at all, overlapping. Super- 

 anal photophores in two groups. Myctophum. 

 Dorsal operlapping anal. Superanals in one or two groups. Benthosema. 

 XX. Head long, limb of preopcrculum oblique, snout conical and snake-like. Pre- 

 oaudal photophores 4 or 2 + 1. 

 Dorsal about equal to or shorter than anal, and not overlapping. 



No orbital spines. Lampanvctvs. 



Orbital spines. Ceratoscopelus. 



Dorsal much longer than anal, and overlapping it. 



Pectorals placed normally. Notoscopelus. 



Pectorals placed very low. Catablemella. 



it. Luminous glands on tail, hid none on head. 

 X. Dorsal and anal nearly equal, not touching same vertical. 



Head somewhat conical, with limb of preoperculum slightly oblique. 

 Saddle-like gland on tail, above and below. Lampahexa. 



Hi. Large luminous glands on head, hut none on tail. 

 X. Superanal photophores in two groups. 

 Precaudal photophores 4. 

 One large, irregular gland occupying entire front of head. ^thoprora. 



Four luminous glands on head, one in front of each eye and one on each infra- 

 orbital. Collettia. 

 Precaudal photophores none. 



A gland in front of each eye below the nostril. 



Photophores and cephalic glands all divided into halves by horizontal septa 

 of black pigment. Diaphts. 



6. Lateral line obsolescent. 



t. No Imninous glands. Photophores much as in li/pical genus. 

 X. Head long, with oblique preopercular limb. 



Dorsal overlapping anal, the latter much the longer. Pectoral very high. 

 Precaudal photophore 1. Apparently no pliotophores un head. 



Tarletonbeania. 

 c. Lateral line with scales much enlarged; scales hard, persistent. 

 I. Luminous glands or scales on top of caudal peduncle ; none on head. 

 X. Scales cycloid. Anal passing behind soft dorsal. 



Body elongate, fusiform; head short, with projecting snout. 



Anal much longer than dorsal, but not overlapping. Caudal peduncle slender, 

 elongate. Stenobrachits. 



One posterolateral photophore over break in superanal series. 



Stenobrachius (Alysia and Khinoscopei.is). 

 Body ovate, compressed; head short, profile declivous; snout not projecting. 

 Anal somewhat longer than dorsal and overlapping it slightly. Caudal peduncle 

 short and stout. 

 No posterolateral photophore. Superanals in unbroken series. Ei.ectrona. 

 XX. Scales ctenoid. Anal terminating below soft dorsal. 



Body elevated, somewhat compressed. Caudal peduncle rather slender. 

 Anal longer than dorsal, but scarcely overlapping. Dasyscopelvs. 



2. Dorsal and anal short, similar, far apart. 



a. Scales large, very deciduous, covered with minute spines. 

 i. No luminous glands on head or tail. 



X. Scales along belly with luminous centers. Photophores far from normal. 

 Head conical; rictus short. 



Dorsal and anal equal, the latter placed with its center under soft dorsal. 



Neoscopelus. 

 !>. Scales (if present) very deciduous, 

 i. Mouth very large; maxillary much dilated at tip. Scopelengys. 



B. Pectorals rudimentary. 

 1. Dorsal and anal overlapping considerablj'. 



a. Liitninoiis glands on tail^ above and below. Photophores minute, irregularly placed. 



