the upper limit of the layer at depths ranging from 50 to 500 m and showed the thickness of the 

 layer to vary from 200 to 1200 m. 



This most interesting problem of interrupted distributions in apparent association with 

 the oxygen minimum should be investigated by the use of depth-selective gear in conjunction 

 with synoptic hydrological observations. Concurrent with that investigation, perhaps some- 

 thing could be learned of the ecology and physiology of those species that must certainly spend 

 much of their lives in this oxygen-minimum layer. 



I have arranged the list of genera and species in alphabetical order mainly for ease in 

 finding the account of a particular species. However, in the text I have followed a phylogenetic 

 arrangement so that illustrations and accounts of related forms could be more juxtaposed than 

 would be possible in a strictly alphabetical order. In general, the phylogeny follows the system 

 proposed by Bolin (1939) and further developed by Fraser-Brunner (1949) — a system based on 

 an ancestor having one or more ventral series of photophores, some of which moved dorsally to 

 form patterns of the modern myctophid while others were presumably lost. I have done so 

 because this study is more concerned with aiding the student in ready identification of species 

 than with following the most recent thought on the phylogeny of lanternfishes. 



I wish to stress, however, that this action is in no way to be regarded as an intent to ignore 

 or disparage the works of Paxton ( 1972) and of Moser and Ahlstrom (1970, 1972, and 1974), in 

 which the arrangement employed by Fraser-Brunner (1949) was significantly altered. I agree 

 generally with Paxton's division of the family into the subfamilies Myctophinae (tribes Myc- 

 tophini and Gonichthini) and the subfamily Lampanyctinae (tribes Diaphini, Notolychnini, 

 Lampanyctini, and Gymnoscopelini). Nor have I any quarrel with Moser and Ahlstrom (1974), 

 who, although in essential agreement with Paxton's suprageneric categories, formulated a 

 somewhat different arrangement based on the sequence of appearance of certain photophores 

 in developing larvae. 



Also, I readily accept the proposal by Moser and Ahlstrom (1972) to consider the species 

 Scopelopsis multipunctatus Brauer ( 1906), a species with minute photophores on each scale 

 pocket of head and body, as representing the ancestral form. These authors stated (p. 562): 

 "Whatever were the adaptive forces that marshalled the light organs of myctophids into 

 specific patterns, we believe that the ancestral myctophids had unspecialized photophores 

 distributed over the head and body (one at the margin of each scale pocket) and that the 

 specific patterns were derived by enhancement of some photophores and the concomitant 

 deletion of others." These authors stated further (p. 563): "Such a mechanism for the evolution 

 of photophore pattern seems much less cumbersome than the theory of upward migration of 

 photophores from the ventral series." 



Most certainly, as the knowledge of these fishes advances, the traditional phylogeny 

 followed here must give way to a more coherent one encompassing larval development, general 

 morphology, physiology, and ecology, as well as taxonomy. 



