Preface xv 



The Keys and other material in these two sections have not been repeated in Parts 4 

 and 5. 



Despite the ever-increasing progress of ichthyology, and of oceanography in gen- 

 eral, and despite the impressiveness of the contents in these volumes, the ichthyologist, 

 and anyone else for that matter who becomes acquainted with the contents here, cannot 

 avoid being impressed with the great gaps in our knowledge of fishes, particularly with 

 regard to the deep-sea groups in Parts 4 and 5. For all the study, observation, and ex- 

 ploration throughout the centuries, our present knowledge is indeed meager when com- 

 pared to what is unknown. Taxonomic descriptions aside, our knowledge of the deep- 

 sea fishes is limited primarily to speculation — to what may be surmised from their shape 

 and color, stomach contents, or location of capture. Of many shallow-water forms we 

 know little more. And even of those that have been subjects of extensive investigation, 

 such as the salmon and some of the commercially important herring-like groups, much 

 of what is known appears to be contradictory or debatable. 



Many species are as yet unknown, and of those now known, many are still re- 

 presented by only one or a few specimens, these often damaged. Not until larger and 

 more extensive collections are assembled will it be possible to clarify the inter-relation- 

 ships of many species and groups, to obtain a more complete knowledge of distribu- 

 tion in area and depth, and much other important information. For the great majority 

 of deep-sea fishes, the records of depth distribution are sparse or crude at best, a 

 lack that stems largely from the fact that most of the deep-sea collections have been 

 taken with open nets rather than closing nets. With the former device, one knows only 

 that a collected specimen frequented some level of the water column between the sur- 

 face and the estimated fishing depth of the net. Even with the closing net, exact depth 

 is questionable because of uncertainties in determining the wire angle. Add to this the 

 fact that the scientific expeditions that have explored the depths have been few and 

 widely dispersed. Considerable areas of all oceans, more so in some than in others, still 

 remain unexplored. 



Even as the present volumes constitute a tribute to the expeditions and countless 

 investigators who have contributed to our present knowledge of fishes, so do they re- 

 emphasize, by what is not known, the need for earnest and continued expansion of 

 marine exploration and investigation, particularly at a time when exploration of the 

 "sea" beyond our atmosphere holds the stage. Especially notable in Parts 4 and 5, 

 dealing mainly with the deep-sea isospondylids and iniomes, are the contributions of the 

 Oregon, Silver Bay, and Combat, whose surveys, sponsored by the U.S. Fish and 

 Wildlife Service, have provided a wealth of study material. Similarly, the contributions 

 of specimens obtained from stomach contents during investigations of the tuna and 

 other commercially important fish have enhanced many accounts; in fact, a number of 

 species, presumably fast-swimming forms that are consistently successful in evading 

 the slow-moving nets, are known only from such a source. Hand in hand with more 

 extensive collecting must go technical development of gear such as closing nets, devices 

 for accurate measurement of wire angle, underwater luminescent and photographic 



