212 SUB-CLASS (AND ORDER) TELEOSTEI. 



There is a considerable number of marine fishes which occasionally 

 wander into freshwater and ascend rivers (e.g. Sciaenidae, Pleuronectes, 

 species of Clupeidae), and a smaller number of freshwater fishes which 

 occasionally descend into the sea (some species of Salmo, of Siluroids, 

 of Coregonus, and pre-eminently the Gastrosteidae and Cyprinodontidae) ; 

 but most of these are inhabitants of the brackish water. They must be dis- 

 tinguished from those fishes which migrate for the purpose of spawning. 

 Such are of two kinds ; there are the anadromous fishes which ascend 

 rivers to spawn in freshwater, as the salmon and the salmon-trout, some 

 Clupeids, etc., and katadromous fishes, like the freshwater eel, which 

 descend to the sea to spawn. There are many clear cases of marine fish 

 which by geological changes have been retained in freshwater basins ; 

 such are Coitus quadricornis, in the large lakes of Scandinavia ; species 

 of Gobius, Blennius and Atherina in the lakes of N. Italy ; Comephorus 

 in the depths of Lake Baikal. 



The classification of the Teleostei adopted here is essentially 

 that of Mr. G. A Boulenger, F.R.S., to whom I am greatly in- 

 debted for having allowed me to see proofs of his work before 

 its publication. It is as follows :* 



Sub-order 1. MALACOPTERYGII (SALMONICLUPEIFORMES).| 



2. OSTARIOPHYSI (CYPRINISILURIFORMES). 



3. SYMBRANCHII (SYMBRANCHIFORMES). 

 4. APODES (ANGUILLIFORMES). 

 5. HAPLOMI (ESOCIFORMES). 

 .. 6. HETEROMI (DERCETIFORMES). 

 , : 7. CATOSTEOMI (GASTROSTEIFORMES). 



Tribe A. Selenichthyes. 



,, B. Hemibranchii. 



C. Lophdbranchii. 



D. Hypostomides. 

 8. PERCESOCES (MUGILIFORMES). 

 9. ANACANTHENI (GADIFORMES). 

 10. ACANTHOPTERYGII. 



Tribe A. Perciformes. 



B. Scombriformes. 



C. Zeorhombi (Zeirhombi formes). 



D. Kurtiformes. 

 . E. Gobiiformes. 



,, F. Discocephali (Echinei former). 



G. Scleroparii (Trigliformes). 



,, H. Jugulares (Blennii formes}. 



* Boulenger, Ann. and Mag. Nat. Hist. (7), 13, 1904, p. 161. 

 t The names in brackets are those used in the fish-gallery of the 

 British Museum. 



