128 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. III. 



north apparently keep to the lowland streams; especially is this 

 true on the Pacific side. The most northern representative of 

 the South American fauna, one of the Cichlida, is found at Maz- 

 atlan. On the east coast this family has a representative in Texas. 

 The fauna of the Lerma, the only river basin extensively studied, 

 is quite distinct from either North or Central and South America. 

 This fauna is richer and more characteristic than was formerly 

 supposed. Almost nothing is known concerning the fishes 

 between the Rio Lerma, the Rio Yaqui and the Rio Grande, 

 An examination of the fauna of the Rio Xazas and other rivers 

 in Central Mexico whose waters never reach either ocean would 

 be extremely interesting. For a study of geographical distribu- 

 tion the fresh water fishes of Mexico are very interesting, perhaps 

 more so than any other animals distributed over a like area. 



