Distribution of Fishes. 2Do 
8. Peculiar and common to South America and Australia— 
Percophididx, Haplochitonide, Galaxiide, and Osteoglossidee. 
9. Peculiar and common to tropical and subtropical America 
and Africa—Cichlide, Characinidee, and Lepidosirenidee. 
In addition to these, the family Cyprinide is represented in 
the entire cistropical or ‘ arctogeean ” hemisphere as well as 
in tropical Africa and Asia ; and there are several monotypic 
families limited to very small regions, such as the Comepho- 
ride, the single species of which is only known from Lake 
Baikal. _ There are, further, a number of families (in addition 
to several already mentioned) which are chiefly represented 
by marine species, but which have also a greater or less 
number of representatives in fresh water in different regions 
of the earth; such are the Brotulide, Blennide, Gobiide, 
Scienide, Atherinide,’ Mugilide, Cyprinodontide, Microsto- 
mide, Clupeidee, Dorosomide, &e. 
Others, again, were represented in former epochs in parts 
of the world where they are not now found; and especially to 
be noted among these are two families at present characteristic 
in their distribution: the first of these is the Cobitidee, which 
in the early Tertiary were inhabitants of Western America, 
and which thus increased the similarity of the fauna of our 
(cistropical) continent to that of Northern Asia; the second 
is the Ceratodontide, a family whose representatives have 
long been known from fossil teeth found in Paleozoic and 
Mesozoic deposits (and which were referred by Prof. Agassiz 
to the sharks), and had been supposed to have expired towards 
the end of the Triassic epoch; yet recently (since 1870) two 
species, closely allied to those found in the Triassic beds of 
Europe, have been discovered “ving in Australia; and thus 
another ancient type has been preserved in that continent to 
illustrate the past life of our own hemisphere. 
If we now seek to apply the knowledge thus gained to the 
appreciation of the origin of the different fish-faunas of the 
globe, we are forced to the following conclusions. 
Inasmuch as the cistropical hemisphere shares in common 
the same families, and to a considerable extent the same 
genera (and even some species), it is presumable that the dif- 
ferent regions of that hemisphere have derived their inhabitants 
from a common primitive source, although North America has 
quite a large proportion of forms peculiar toit. ‘The relation 
of these peculiar forms, however, are in all cases rather with 
some found in the northern hemisphere (freshwater or marine) 
than with any found elsewhere; but, at the same time, towards 
the south-western limits of the United States occur repre- 
sentatives of families which are characteristic of tropical 
Ann. & Mag. N. Hist. Ser. 4. Vol. xv. 18 
