SOUTH AMERICAN FISHES 



27 



and we have the following possibly independent lines of evolu- 

 tion to attain the scaled condition. 



Caudal nalcd Caudal sculod. 



Hypliessobrycoii 1 leiiiii^rainiinis. 



Astyanax r Mooiikliausia-'lY^ragoiiopterus- 



ancl J Eiitomolepis-Gymonocorymbus- 



Poeciluriclitliys Tliayeria and Pristella. 



Bryconamericns Knodus. 



The change from a naked candal to a scaled one seems to be 

 at present taking place in Astyanax toiniatus, and in some of the 

 smaller species of Hyphessobrycon. 



None of the numerous other genera have crossed the line, and 

 this character seems to be more firmly established since the group 

 of genera centering in Moenkhausia have all evolved since the 

 scaled caudal has developed. It is, in fact, quite possible that 

 the differentiation into a group with a scaled caudal and another 

 with a naked caudal is a primitive change ; that the- line has been 

 crossed but once ; and that Hemigrammus and Knodus with scaled 

 caudals have converged in their other characters to Hyphesso- 

 brycon and Bryconamericns with naked caudals. 



Teeth appear to have developed along the entire edge of the 

 raaxillary from a few along the upper corner, as follows: 



With a few teeth With teeth aloiif/ the entire inaryin 



Hemigrammus iPristella. 



Brycenamericiis Hemibryccn, Hollandicbthys, and Psendocbalcens. 



? Pbenacogaster and Vesica trns. 



Astyanax a?neus Astyanax nicaraguensis. 



The change is now being made in Astyanax nicaraguensis, 

 ^Ahich has more than the usual number of teeth (as many as 11) 

 found in its relatives. 



Concerning several species of B.emibrycon, dccurrens, diquensis, 

 hoquice, tolimce and colomhianus, it may be said that they are 

 members of the genus Bryconamericns with extreme development 

 of maxillary teeth, or members of the genus Hemibrycon with the 

 minimum development of maxillary teeth. They are, in short, 

 intermediate in character. 



The method by which a single series of teeth has in a number 

 of instances given rise to, or is giving rise to, a double series is 

 illustrated by the genera: 



Coeliiriebtbys 

 Cbalcinus 



Gasteropelecns into Tboracocbarax. 



