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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 ;
ranges from India to Borneo.
Chacina (1 genus, Chaca)
Sub-family 2 (Silurid^ Heteropter^) is also confined to the
Old World ; it consists of one group,—Silurina, containing 19
genera, viz. :
Ceylon ;
Saccohranchus (4 sp.), India to Cochin China and
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