32 A JOURNEY IN BRAZIL. 
hemisphere the latter extend from the high north to Texas, 
south of which they are represented by the Chromids. Here 
the geographical as well as the structural transition would 
seem an easy one. But look at the eastern hemisphere. 
Perches abound in Asia, Europe, and Australia, but there 
are no Chromids there. How is it that the Perches of this 
continent have been so fertile in producing Chromids, and 
the Perches of all other continents, except Africa, absolutely 
sterile in this respect ? Or if we reverse the proposition, 
and suppose the Perches to have grown out of the Chromids, 
why have their ancestry disappeared so completely on the 
Asiatic side of the world, while they do not seem to have 
diminished on this ? And if Perches and Chromids should 
be represented as descending from an older common type, 
I would answer that Paleontology knows nothing of such a 
pedigree. 
" Next come the Chubs, or in scientific nomenclature the 
Cyprinoids. These fishes, variously called Chubs, Suckers, 
or Carps, abound in all the fresh waters of the northern 
hemisphere. They are also numerous in the eastern part 
of the southern hemisphere, but have not a single represent- 
ative in South America. As the Goniodonts are charac- 
teristic of the southern hemisphere in its western half, so 
this group seems to be characteristic of it in its eastern 
half. But while the Cyprinoids have no representative in 
South America, there is another group there, structurally 
akin to them, called the Cyprinodonts. They are all smalL 
sized ; our Minnows belong to this group. From Maine to 
Texas they are found in all the short rivers or creeks all 
along the coast. It is for this reason that I expect to find 
the short coast rivers of South America abounding in Min 
nows. I remember to have found in the neighborhood of 
