THE AMERICAN TETRAGONOPTERINAE. 43 



possibly the most primitive member, of the subfamily. Poecilurichthys, which 

 differs from it only in having the character I instead of L, is scarcely distin- 

 guishable. 1 



The different characters of the first column are found in various combina- 

 tions with most of the characters of the second column. Thus A is found in 

 combination with all (not counting its contrasted character, a) except k and I. 

 B is found in combination with all but o and p. C is found in combination with 

 all the characters of the second column and the same is true of all the rest of 

 the characters of the first column. 



POLYPHYLETIC CHARACTERS. 



It is quite certain that the characters of the right-hand column of the 

 contrasted generic characters have sometimes, at least, been independently 

 derived from the characters of the left-hand column, not only by the different 

 genera possessing the character, but sometimes by different species of the same 

 genus. That is, some of the genera possessing characters given in the second 

 column are of polyphyletic origin. 



Beginning at the bottom of the list, the character o is found in Hasemania 

 from southeastern Brazil, and in the very different genus, Nematobrycon, 

 from the west of the western Cordilleras of Colombia. The two genera are not 

 related, and are widely separated geographically. There can be no doubt but 

 that they have independently lost the adipose fin. 



The next undoubted case is that indicated by g. This character is found 

 in Poecilurichthys, scarcely distinct from Astyanax, and in Gymnocorymbus, 

 a very different fish. Here again the character has very probably been inde- 

 pendently acquired by the two genera. 



1 In Indiana Univ. Studies, 1914, No. 20, I have tried to carry the inference a step further. 



"The common possessions of all members of the Tetragonopterina; enumerated above, permit us 

 to picture the ancestral type of the subfamily. In brief, it must have been a fish similar in most char- 

 acters to Astyanax fasciatus Cuvier. This species, besides possessing all the characters common to all 

 members of the subfamily, possesses also many of those positive (as contrasted with absent) characters 

 enumerated for the family, and lacks some characters, like the highly specialized scaling of the ventral 

 surface, ctenoid scales, extreme length of anal, extreme development of second suborbital, which are 

 evidently highly specialized characters in a few of the genera. It is more widely distributed than any 

 other species and has given rise to numerous variations. 



It represents an average in length of head (4.3), depth, (2.6-3); length of anal (about 30); scales 

 (about 38); size of eye (2.5-3); general shape (compressed subfusiform) ; position of dorsal (its base 

 being in the space above the origins of the ventral and anal) ; size of mouth ; and the characters of the 

 teeth. The fossil fishes found at Taubate — south of Rio de Janeiro — are similar to it in most char- 

 acters. They are a little larger and may be members of the genus Brycon. In all but the teeth, they 

 are very similar to Astyanax fasciatus." 



