﻿ElGENMANN '. FlSHES OF WESTERN COLOMBIA 



7 



The Fishes of the San Juan. The knowledge of the fauna of 

 the San Juan is based on collections made by Spurrell and Car- 

 penter, reported upon principally by Regan (Ann. and Mag. 

 Nat. Hist. (8) XII, Nov., 1913, pp. 462-473 and XIV, July, 

 1914, pp. 31-33) ; on collections made by myself at Puerto Negria, 

 a point half-way to Istmina, and at Istmina ; by Wilson at 

 Puerto Xegria, Istmina, Condoto ; and by Henn, between Puerto 

 Xegria and the mouth of the Calima, and in the Calima river to 

 near Buenaventura. While the river has not been exhausted we 

 know all of the main features of the fish fauna of this river. 



A Comparison of the Fish Faunas of the Atrato and San Juan. 



In the Atrato and San Juan there are now known 112 species of 

 fishes. Only 31 or about 28 per cent of these are common to the 

 two rivers. 6 



In the Atrato alone 72 species have been observed, in the San 

 Juan alone 71 species. The 31 species 6 common to the Atrato 

 and San Juan form about 44 per cent of the entire San Juan 

 fauna. Of the fishes inhabiting the San Juan and other west 

 coast streams 42 species have not been taken in the Atrato. 



The species common to the Atrato and San Juan basin belong 

 to one of four groups : 



A. Those common both north and south of the San Juan. 



B. Those common north of the Atrato, finding their furthest south 

 in the San Juan. 



C. Those common south of the San Juan, finding their furthest north 

 in the Atrato. 



D. Those confined to the two rivers. 



A. To the first of these classes belong Rhamdia wagneri, Chae- 

 tostomus fischeriy Sturisoma panamensis, Hyphessobrycon pana- 

 mensis, the latter represented by different varieties in the north 

 and south, Hoplias malabaricus, Stemopygus macrurus. Of these 

 only the first and last are found as far south as the Rio Ouayas. 



B. Those common north of the Atrato 7 which find their furth- 

 est south in the San Juan, and which probably migrated south, 

 are Loricaria variegata, Fiabucina panamensis, Astyanax fascia- 

 tus, Creagrutus affinis, Thoracocharax maculatus, Gtenolucinus 

 beani, Rivulus elegans, Aequiclens latifrons, Gymnotus carapo. 



6 A number of species recorded from the San Juan and Magdalena but not hither- 

 to taken in the Atrato might with reason be added to the 31, swelling- the total to at 

 least 36. 



7 As stated elsewhere, the territory in the Atrato basin which may be expected to 

 harbor species of Pygidium and Astroblepus has not been examined. 



