FISHES. 139 



The Paealbpidid^e are small deep-sea fishes allied to the Alepidosauridse. They 

 are baiTacuda-like in form and dentition, the body being slender, the teeth strong and 

 some of them fang-like. The dorsal fin is short and far back, and there is an adipose 

 fin behind it. The known species are about five in number, from the waters of 

 Europe and America. One of these {Sudis rincjens) is known only from a single 

 specimen found by the present writer in the body of a hake (Merlucms prodtcctus), 

 the hake in turn having been swallowed by an albicore {Orcyniis alalonga), and the 

 latter taken on the hook, before the Sudis inside the hake had become digested. 



The SYNODONTiDiB or lizard-fishes, have the body elongate and nearly cylindrical, 

 covered with scales, as are also the sides of the head. The head is lizard-like in form, 

 the gape of the mouth very wide, and the jaws are armed with many rows of sharp 

 teeth. The maxillary is very slender or nearly obsolete, and closely adherent to the 

 premaxillary. This character best distinguishes the family from the Scopelidse and 

 other forms, in which the maxillary is well developed. The dorsal is short and 

 median in position, and behind it is usually a well-developed adipose fin. The skele- 

 ton is more perfectly ossified than in related families. 



There are about twenty species known, inhabiting the seas of warm regions ; vora- 

 cious fishes of little value as food. A few of them are deep-sea forms, but the most 

 of them inhabit shallow waters, in which they lie close to the bottom, their colors 

 often very closely imitating the coral-sand and algae. One species, Sy7iodi(,s fcetens, is 

 abundant on our South Atlantic coast, and others occur further southward. 



The AuLOPiD^ are closely allied to the Synodontidse, differing in the well-devel- 

 oped maxillary, and, according to Cope, in the presence of a tail vertebra. The few 

 species are found in the Mediterranean and in the Pacific. 



The ScoPELiDiE are also allied to the Synodontidfe, but have the maxillary well 

 developed, the body more compressed, and in nearly every species provided with 

 jjhosjAorescent spots. Some fifty species are now known, most of them deep-sea 

 fishes, although others are rather pelagic, some of them (Myctophum) " coming to 

 surface at night only ; during the day and in very rough weather, they descend to 

 depths where they are safe from sunlight or the agitation of the water." {Qiinther.) 

 Some of them may be caught in the night by a tow-net at the surface, while others 

 are found at a depth of nearly three miles. One of the American species {Mycto- 

 phum crenulare) is known from two specimens only, the one taken from the stomach 

 of an albicore {Orcynus), in the Santa Barbara channel; the other thrown by the 

 waves, in a storm, on board a vessel in the Strait of Juan de Fuca. The most 

 remarkable j)eculiarity of the Scopelida3 and related deep-sea forms is the develop- 

 ment of luminous spots. These are usually arranged in one or more series along 

 the sides of the body. 



Closely related to the Scopelidffi are the Ipnopid^, consisting of the single genus 

 Ipnops. In this genus the whole upper surface of the long snout is occupied by a 

 phosphorescent organ, longitudinally divided into two symmetrical halves. This is 

 apparently the representative of the eye, and it is thought by Dr. Glinther, who 

 first described Ipnops murrayi, that the eye has " lost its function of vision and 

 assumed that of producing light." 



The following account of the structure and functions of the phosphorescent spots is 

 condensed from the chapter on deep-sea fishes in Gtinther's Guide to the Study of Fishes. 



Many fishes of the deep sea are provided with more or less numerous round, shin- 

 ing, mother-of-pearl-colored bodies, imbedded in the skin. These so-called phosphor- 



