CHAP. XX.] FISHES. 441 



Seven genera occur in British seas, viz. : Hippoglossus, Hippo- 

 glossoides, Rlwmbus, Phrynorhomhus, Arnoglossus, Pleuronectes 

 (Turbot), and Solea (Sole). There are 13 genera in the Atlantic 

 and 23 in the Pacific, 4 being common to both ; and 2 found 

 only in the Mediterranean. A Pacific genus, Synaptura, has 

 one species in the Mediterranean. 



Order IV.—PHYSOSTOMI. 



Family 59.— SILUKID^. (114 Genera, 547 Species.) 



" Fresh-water or marine, scaleless fishes, often with bony 

 shields, and the head always furnished with barbels." 



Distribution. — The fresh waters of all the temperate and 

 tropical regions, those which enter the salt water keeping near 

 the coast. 



This extensive family is divided by Dr. Giinther into eight 

 sub-families and seventeen groups, the distribution of which is 

 as follows : — 



Sub-family 1 (Siluhid^ HoMALOPTERiE) is confined to the 

 Old World. It consists of three groups : Clarina (2 genera, 

 Glarias and Eeterohranchus) ranges over the whole area of the 

 Ethiopian and Oriental regions, to which it appears to be strictly 

 confined ; Plotosina (3 genera, Plotosus, Copidoglanis, and Cnido- 

 glanis) ranges from the eastern coasts of Africa to Japan, Poly- 

 nesia, and Australia, in seas and rivers ; Chacina (1 genus, Chaca) 

 ranges from India to Borneo. 



Sub-family 2 (Silurid^ Heteropter^) is also confined to the 

 Old World ; it consists of one group, — Silurina, containing 19 

 genera, viz. : — Saccohranchus (4 sp.), India to Cochin China and 

 Ceylon ; Silurus (5 sp.), Palsearctic region from Central Europe 

 to Japan, China, and Afghanistan, and a species in Cochin China; 

 Silurichthys (3 sp.), Cashmere, Java, and Borneo ; Wallago (2 sp.), 

 Hindostan, Sumatra, and Borneo ; Belodontichthys (1 sp.), Su- 

 matra and Borneo ; Eutropiichthys (1 sp.), Bengal ; Crypiopterus 



