D CALIFORNIA ACADEMY OF SCIENCES. 



Seven of these families are confined to tropical 

 America. 



In several cases the gradation from one family to 

 another is so gradual that the present classification may 

 be looked upon as provisional. The inter-relation of the 

 families and their subfamilies is illustrated in the dia- 

 gram on opposite page. 



The general distribution of these families and their 

 subfamilies is as follows: 



I. BUNOCEPHALID^E Amazons from Para to Pebas, 



Nauta and Canelos; Guianas. 

 BUNOCEPHALIN^E Solimoens, Maranon; Guiana. 

 PLATYSTACIN^E Amazon; Guiana. 



II. DIPLOMYSTIDJE Chile. 



III. SILURID.E Cosmopolitan. 



TACHISURIN^E Atlantic and coast rivers from La 

 Plata to North America; Pacific, from Callao to 

 Mexico; Africa, Asia. 



CALLOPHYSIN^: Amazons to Calderon; Guiana. 



PIMELODINJE Eastern rivers from La Plata to 

 Mexico; western rivers from Callao to Mexico; 

 Africa. 



DORADIN.E Rio Plata; Rio San Francisco to Peru 

 and Colombia. Not in Rio Parahyba, Rio Doce 

 or Jequitinhonha. 



AUCHENIPTERIN^E Rio Janeiro to Rio Magdalena 

 and Peru. 



AGENEIOSIN^E La Plata; Rio Paranahyba, to Guiana 

 and Peru; not in Rio Parahyba, Doce or Jequi- 

 tinhonha. 



IV. HYPOPHTHALMID^D Amazons from Para to Rio 



Huallaga; Guiana region. 



V. PYGIDID^E Chile and Argentine Republic north to 



Colombia; chiefly in mountain streams. 



