TENTATIVE ARRANGEMENT OF THE GENERA OF MYCTOPHIDJE. 



I. Hody oljlono;, compressed. Teeth in jaws in villifoiiu l)anils. 



A. Pectorals present. 



1. Diii'.sal ami anal fins touclun<^ (or nearly so), the same vertical, or overlapping. 



a. Lateral line not at all, or bnt slightly, enlarged. Scales cycloid, smooth. 



i. Xu Inminoiis ijlanih on head or tail. { Luminous srnles Komctimra prrnenl on toil, dliore or 

 Inlow.) 

 X. Head short, witli limb of jireopercnlnm nearly vertical; snout more or less blunt 

 and declivons. Precaudal photophores 2. 

 Dorsal entirely in front of anal, and scarcely, or not at .'ill, overlapping. Superanal 



photophores in two groups Myctophum 



Dorsal overhijiping anal. Su])eranals in one or two gronps Bexthosema 



XX. Headlong, limb of preoperculum oblique, snout conical and snake-like. Precaudal 

 ])liotophore8 4 or 2+1. 

 Dorsal about equal to or shorter than anal, an<l not overlapping. 



No orbital spines Lampan YCTUS 



Orbital spines Cekatoscopelus 



Dorsal much longer than anal, and overlapping it. 



Pectorals placed normally Notoscopelus 



Pectorals placed very low C at.vblemella 



ii. Lnminoiis gJiiiidx on tail, bnt none on head. 



X. Dorsal and anal nearly ecjual, not tonching same vertical. 



Head somewhat conical, with liml) of ]>reoperculum slightly oblique. 



Saddle-like gland on tail, above and below LAMPADE>fA 



iii. Lartje Inminons (/lands on head, hnt none on tail. 

 X. Superanal photophores in two groups. 

 Precaudal photophores 4. 



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



h'onr luminous glands on head, one in front of each eye and one on each 



infraorbital 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 Diaphus 



b. Lateral line obsolescent. 



i, Xo Inminons {/lands. Photophores mweh as in ti/pical genus. 

 X. Headlong, with oblicjuo preojiercular limb. 



Dorsal overlapping anal, the latter much the longer. Pectoral inserted high up. 

 Precaudal photophore 1. Apparently no photophores on head.TARLETONBEANiA 



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



i. Liiminons glands or scales on top of candal peduncle; none on head. 

 X. Scales cycloid. Anal passing behind soft dorsal. 



Body elongate, fusiform; head short, with i)rojecting snout. 



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

 elongate. 

 One posterolateral photophore over break in superanal series. 



Rhinoscopelus 

 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. .Electrona 

 XX. Scales ctenoid. Anal terminating below soft dorsal. 



Body elevated, somewhat compressed. Caudal peduncle rather rlender. 



Anal longi'r than dorsal, but scarcely overlapping Da.syscopelus 



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



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

 i. Xo Inminons glands on head or tail. 



X. Si'ales 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. 



Neoscopei.us 

 b. Scales (if present) very deciduous. 



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



B. Pectorals rudimentary. 



1. Dorsal and anal overlapping considerably. 



a. Lnniinous glands on tail, above and below. Photophores minute, irregitlarhi placed. 



i. Head long, with oblique preopercular limb; snout conical; mouth terminal, hori- 

 zontal Xannobrachium 



II. Body elongate, cylindrical. Teeth in lower jaw in several series Scopelosaurus 



