64 



As permaneut gill-beaiiug Batmchia, Necturm represents the Palae- 

 arctic Proteus^ aud Siren is quite peculiar to North America. The 

 Amphiuma, or snakelike Batrachia, calls to mind the similar extinct 

 forms of the Coal-Measures ; while Protonopsis is represented by living 

 species in Eastern Asia, aud by a fossil genus in the Miocene of Ger- 

 many. 



The marine fishes embrace some species which range both coasts 

 of the North Atlantic. Such are the salmon, the haddock, the mackerel, 

 etc., which furnish food and occupation for a numerous population on 

 the northeastern coast. Farther south, the mullet [Mugil albula) is a 

 valued food-fish, and is caught and packed in great numbers. The 

 fishes of the Pacific coast are mostly distinct from those of the Atlantic, 

 except a few circumpolar forms, as Oasterosteus aculeatiis ; but several 

 (as Gadus vachna, Pall.) are found also on the Asiatic coast. On the 

 warmer coasts, a few species are common to both oceans, while others 

 exist which have a great range over several seas, noticeable among 

 which are certain species of Plectognathi, particularly of Diodon, Ba- 

 listes, etc. 



The freshwater fishes embrace many families characteristic of the 

 northern hemisphere, as the cods [Gadidae], Percidae or perch, the scul- 

 pius {Cottidae), pike [Esocidae), chubs (Cyprinidae), the salmon, and 

 herring, eel, sturgeon, and lamprey families. In the catfishes, the 

 region reminds us of the tropical and southern regions ; though it is a 

 singular fact that one of our genera {Afniuriis) is represented by single 

 species in China. 



The suckers (Catostomidae) are very abundant and characteristic in all 

 fresh waters; but here, again, a single species [Carpiodes sinensis) has 

 been detected in China. This is paralleled by the genus Polyodon (pad- 

 dle-fish), of which one species is found in the Mississippi Valley, and 

 one in the Yang tse-kiang. The most striking peculiarity of the Nearc- 

 tic waters is the presence of the family of Lepidosteidae, or bony gars, 

 which is represented by two genera and numerous species. No form at 

 all resembling these exists in any other country, excepting again one 

 species in China, and one other which is found in the adjoining Neotrop- 

 ical region. Not less peculiar are the species of dog-fish {Aniia), type.of 

 the order HalecomorpM, which have some remote affinities with South 

 American forms. 



The relations to the Neotropical realm are in part indicated in the 

 table on page 57. But few species are common to the Nearctic and 



