82 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 Palaeontology 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 



