Jordan and Evermann. Fishes of North America. 551 



Species about 100, placed in one genus by Giinther and Liitken, divided 

 into many by Goode & Bean. Small fishes, very widely distributed in 

 the open sea. They live away from the shores, ordinarily at a consider- 

 able depth, coming to the surface at night or in stormy weather, descend- 

 ing by day. 



Until the recent review of the Mediterranean species by Raffaele and 

 especially the admirable monograph by Dr. Liitken (Spolia Atlantica, 

 part 2, 1892), the species were very imperfectly known. This masterly 

 paper of Dr. Liitken has been followed by a very exhaustive account of 

 the Atlantic species by Goode & Bean (Oceanic Ichthyology). Advance 

 sheets of this paper have been kindly placed at our disposal by its authors, 

 and our manuscript has been entirely recast to include the species there 

 described. Liitken places the species in one genus, Scopelus, but " for 

 convenience of study and comparison " Goode & Bean have thought it 

 " best to break up this great polymorphous genus" into minor groups. 

 We find, however, considerable difficulty in giving these smaller genera 

 satisfactory definition, but on the whole we have found it more con- 

 venient to recognize them as distinct genera rather than to place them 

 as subgenera under the common head of Myctophum. The extreme ranges 

 of variation are greater than are usually recognized as occurring within 

 the limits of a natural genus. 



NOTE. Dr. Kaffaele and Dr. Liitken have shown the great importance of the position of the 

 luminous spots or photophores as characters distinguishing the species of Scopelidse. Dr. Liitken 

 has proposed a system of nomenclature for them, as follows: 

 Caudal (or precaudal) spots or photophores, those 2, 3, or 4 in number at or near base of lower 



lobe of caudal, the first separated by a break from the anal series. 

 Anal spots, those forming a series from vent along base of anal and caudal peduncle; this series 



is usually interrupted above last part of anal, one or two spaces being without spots. 

 Posteroluteral spots, or spots placed near the lateral line above the break in the anal series. 

 Supra-<~.Ml spots, usually 3 in number, forming an oblique series or a triangle between vent and 



lateral line. 



Ventral spots, a series of 4 or 5 between ventrals and vent. 



Supraventral, a single spot sometimes present between ventrals and lateral line. 

 Thoracic spots, a series, often irregular, of about 5, along breast. 

 Pectoral spots, usually about 3, about base of pectoral. 

 Opercular, 2 or 3 on opercle. 

 Handibular, about 3 on mandible. 



Besides these, preocular, sabocular, supracaudal, and infracaudal luminous patches often occur. 

 The luminous glands on tail are so often obsolete as to lose much of their value in classification. 

 In this paper we have adopted in the descriptions written by us, the nomenclature of Dr. Liitken 

 as above given. In the descriptions copied from Goode & Bean a somewhat different system is 

 used, but we have preferred not to alter the language of these authors. 



NOTE. Goode & Bean (Oceanic Ichthyology) offer the following 



TENTATIVE ARRANGEMENT OF THE GENERA OF MYCTOPHIDJE. 

 J. Body oblong, compressed. Teeth in jaws in villiform bands. 

 A. Pectorals present. 



1. Dorsal and anal fins touching (or nearly so) the same vertical, or overlapping, 

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



i. No luminous glands on head or tail (Luminous scales sometimes present on tail, above or 



beloiv.) 



x. Head short, with limb of preoperculum nearly vertical; snout more or less blunt 

 and declivous. Precaudal photophores 2. 



