BONY FISHES AND GANOIDS. 505 



tergissus), and a small fish (Pantodon bitcholzi) remarkably like a cyprinodont, 

 from West Africa, severally represent two families. From 

 the foregoing families of the section, these two groups are Families 



distinguished by the under-mentioned characters. The ffyodontidm and 

 pterotic bones are of normal conformation ; there are four Pantodonlidm. 

 separate upper pharyngeal bones, of which the third and 

 largest is directed forwards ; and the base of the skull is double. All these 

 features are common to the remaining families of the section. In the Hyo- 

 dontidcB the two parietal bones are united together, and the bony structure 

 supporting the tail-fin is preceded by two true caudal vertebrae. Whereas in 

 the moon-eye the tail is deeply forked, in Pantodon it terminates in a point. 

 A long slender fish from the seas of Australia, Japan, and 

 South Africa, known as the beaked salmon (Gonorhynchus Family 



greyi), likewise constitutes a separate family, distinguished Oonorhijnchidm. 

 from the last two by the presence of barbels to the mouth, and 

 the absence of true caudal vertebrse. The beaked salmon varies from a foot to a 

 foot and a half in length, and is often found in sandy bays. Its flesh is eaten. 

 The three families now to be mentioned include marine fishes, of which the 

 majority are deep-sea or pelagic in their habitat, while many are remarkable 

 for the development of special phosphorescent organs, by the 

 aid of which they find their way in the dark ocean abysses. Families 



From the preceding family, the Scopelidie are distinguished Scopelidce, 

 by the absence of barbels, and of spines on the scales (when Sternoplychidce , 

 the latter are developed), and the presence of a small and Stomiatidce. 

 fatty fin posterior to the dorsal. Whereas some forms are 

 scaled, others are naked ; but all are characterised by the wide gill-opening, 

 the possession of false gills, the absence of an air-bladder, and the formation 

 of the margin of the upper jaw by the premaxillse alone. A peculiarity of 

 these fishes is the extreme shortness of the intestine. The typical genus 

 Scopelus includes fishes of normal form, with rows of phosphorescent spots on 

 the lower side of the body ; but in Ipnops the whole body is exceedingly long 

 and slender, and the upper surface of the flattened head occupied by a large 

 luminous organ. Other genera are Saurus, Pamleyis, Plagyodus (in which 

 the body is naked, and the jaws are armed with large tusks), and Gymno- 

 scopelus, in which scales are likewise wanting. Of the other two families it 

 will be unnecessary to give all the characters, but it may be mentioned that 

 in the Sternoptychidm the fatty fin is either very small or rudimental, while 

 there are no barbels, and the body may be either naked or covered with thin 

 deciduous scales, while the maxillae enter into the margin of the upper jaw. 

 On the lower parts, light-organs are developed. One of the best-known 

 forms is the somewhat elongated Photichth ys, from which the allied Cliauliodus 

 difiers by the large size of its teeth. On the other hand, the typical Ster- 

 noptyx has the body deep and compressed, and the tail short. The Stomiatidce 

 differ by the presence of a long barbel attached to the hyoid bone, which 

 depends from the lower jaw, the fatty fin being often totally wanting. 

 Astronesthes, which is one of the genera with a small fatty fin, has a large 

 head, and jaws armed with powerful teeth. Stomias and Echibstoma both 

 lack the fatty fin, but whereas the former has the body covered with minute 

 scales, in the latter the skin is naked, and the small pectcjral fins have some 

 of their rays prolonged into thread-like filaments. At times the deep-sea 

 fishes of the pijesent group are met with floating in a helpless inert condition 

 on the surface of the ocean ; but they are generally only obtained by 



