642 Sexual Differences in Piecilud Fishes. 



longitudinal series. Similar to C bellottii in form and 

 coloration in both sexes ; back in front of dorsal fin arched, 

 bearing a series of bony tubercles; head boiiy^ ^vith post- 

 orbital tubercles. 



Province of Buenos Aires. 



Total length 85 mm. 



2. CynoJebias hulmberrji. 

 Berg, t c. p. 296. 



S. D. 21, A. 25 ; ? . D. 17, A. 21. At least 60 scales 

 in a longitudinal series. Head 3^ to 3^ in length to base of 

 caudal. Yellowish ; a dark bar on the head. 



Province of Buenos Aires. 



Total length 300 mm. 



In C. melanotcenia the males are similar to the females both 

 in coloration and in number of fin-rays ; in this species the 

 pelvic fins are separated by an interspace, whereas in Cyno- 

 lebias proper they are contiguous and often united at the 

 base. I therefore propose to make C melanotcenia the type 

 of a new genus, which may be named Cynopcecilus. 



I have ascertained that the types of C. rohustus and 

 C niyripinnis are males ; the single example of C. elunyatus 

 in the British Museum collection has been eviscerated, but 

 it seems probable that the two or three specimens known of 

 this species are females, whilst the type of C. porosus may be 

 a female also. 



Assuming this to be the case, the number of scales in a 

 longitudinal series, and of dorsal and anal rays in both sexes, 

 of the species of Cynokbias may be tabulated as follows : — 



Scales. c? . 5 , 



