18 ^Ir. C. T. Regan on the 



Ih'stichodus lias fontanels, but Nannocharax lias not ; Ilemi- 

 odus has fontanels, but Farodon has not ; most species of 

 Alestes have fontanels, but in Alesles macrolepidotus they are 

 absent and the parietals are united by suture. I could give 

 other examples, but these will suffice. 



Chalceus has the mouth and dentition of Brycon and is 

 certainly related to that ,2;enus ; on the other hand, the hirge 

 scales, the short anal fin, the tiattish head, &c. suggest 

 relationship to Pyrrhulina, which is confirmed by the large 

 size of the mesethmoid bone and by the somewhat inter- 

 mediate dentition of PletJwdectes. 



Another genus with the mouth and dentition of Brycon is 

 Chalcinus, which differs chiefly in the keeled thorax and 

 compressed abdomen ; on this account Eigenmann associates 

 it with Gastropelecus, but the skeleton is essentially similar 

 to that of Brycon, Pseiidocorynopoma differs rather markedly 

 from Chalcinus, and appears to me more nearly related to 

 Astyanax. In Paragoniates and Leptagoniates the keel of 

 the thorax is evident, but the abdomen is not compressed to 

 a sharp edge ; these appear to me to be related to Ilemi- 

 hrycon and Aphyocharax respectively, whilst Piahuca may 

 stand in the same relation to Odontostihle that Chalcinus does 

 to Brycon. 



From the above remarks it will be evident that I do not 

 regard Eigenmann''s Gastropelecinje and Agoniatinae as 

 natural groups, and the same may be said of his Characina?, 

 which includes three well-marked groups which are not 

 specially related, viz. (1) Bramocharax, (2) Sahninus and 

 IJystricodon, and (3) Charax, lioeboides, and Cynopotamus. 



Bramocharax is, in my opinion, closely related to Scissor; 

 the latter is a Tetragonopterus with large mouth, produced 

 snout, enlarged anterior teeth, and outer seiies of prjeuiaxillary 

 teeth reduced ; Bramocharax seems to differ only in that the 

 snout is longer, the enlarged anterior teeth are further apart, 

 and the outer pri\3maxillary teeth are still smaller. Sahninus 

 and llystricodon are closely related to Brycon, from which 

 they differ only in the dentition ; moreover, most of the 

 teeth in Salminus are not truly conical, but approximate to 

 the compressed and tricuspid type, especially in young 

 specimens; Agoniates is known to me only from the descrip- 

 tion and figure of Miiiler and Troscliel, but I believe that it 

 will prove to be closely related to Sahninus. 



Charax, Roeboidcs, and Cynopotamus, with their exposed 

 maxillary and long anal fin, show little resemblance to Sal- 

 minus, but much to Jleniihrycon and Pa7\igoniates, to which 

 they are probably rather closely related. 



