254 On the Geographical Distribution of Fishes. 
‘America. Further, it is to be remarked that several of those 
forms whose living ‘representatives are most characteristic and 
peculiar to North America, e.g. Amide and Lepidosteide, 
were in previous geological epochs represented by species in 
Kurope; while the Cobitide, now unrepresented by living 
American species, had, as already remarked, examples in more 
ancient times in that continent. 
Tropical Asia nourishes a great number of peculiar forms ; 
but the relations of those are intimate either with cistropical 
ones or with marine types. 
Africa has Cyprinoids and Anabantids in common with 
tropical Asia, and Cyprinoids in common with the cistro- 
pical hemisphere; but it also supports several very peculiar 
families for whose relations we have to seek in other con- 
tinents. 
In tropical America are to be found the nearest relations of 
some of these African types, and several almost or quite 
limited to those two comtinents. On the other hand, in South 
America are found several families having no analogues in 
the parts of the world yet mentioned, but for which we have 
to turn our eyes to Australia ; and there we have representa- 
tives of not only the same families, but even, it has been con- 
tended, one of the same species. Under these circumstances 
we are almost compelled to believe that the fish-fauna of 
South America was derived, at a distant epoch, to some ex- 
tent from a common source with that of Africa and that of 
Australasia. We have, however, at first sight, contrary in- 
dications; but they are not irreconcilable: the most conspicuous 
and, as it were, obtrusive types of South-American fishes are 
analogues of African forms, members of the families Cichlide 
and Characinide ; but the species belong to widely different 
genera. On the “other hand, although the types common to 
South America and Australia are not conspicuous In numbers 
or economical importance, they are much more nearly related 
to corresponding Australian species than the former, and, in 
common with other facts, tend to verify Huxley’s views 
respecting an “ Austro-Columbian ”’ fauna. 
In fine, dividing the earth into regions distinguished by , 
general ichthyological peculiarities, several primary combina- 
tions may be recognized, viz. :—1, an Arctogean, embracing 
Europe, Northern Asia, and Northern America; 2, an Asiatic, 
embracing the tropical. portions of the continent ; 3, an Afri- 
can, limited to the region south and east of the Desert : 4,an 
American (embracing the America par eacellence dedicated to 
Amerigo Vespucci), including the tropical and transtropical 
portions ; and, 5, an Australasian. Further, of these (a) the 
