108 MEMOIRS OF THE CARNEGIE MUSEUM 



In different species of the Nannostomatince, Tetragonopterince and the Chara- 

 cince the pectoral has at times been arrested in its normal development. It has 

 retained the embryonic form. Inasmuch as I had never seen a similar condition 

 in other fishes the first specimen was described as a distinct genus. Mrs. Ellis 

 at once found another. Mrs. Ellis then made a systematic search for similar mu- 

 tants in the large collections made, not only bj' myself, but also among the Tetra- 

 gonopterince collected by Mr. Haseman in various parts of Brazil. She reports: 



The specimens with an archaic pectoral were forty-four in number, belonging 

 to eight different species of five different genera and three different subfamilies, 

 as follows: 



Archicheir mimitus Eigenmann, one specimen, 26 mm., Christianburg (Car- 

 negie Museum Catalog of Fishes No. 1186). 



Dermatocheir catablepta Durbin, one specimen, 18 mm., Tumatumari, British 

 Guiana (C. M. Cat. No. 1198). 



Hyphessobrycon parvella Mrs. Ellis, one specimen, 18 mm., Riberao, Azula 

 Lagoa (C. M. Cat. No. 2930); one specimen, 12 mm., Rio Tiete (C. M. Cat. No. 

 2931), with archaic pectorals. Thirteen specimens, 13 to 29 mm. (No. 2932), 

 Aqua Quente, Alagoinhas, Rio Catu, Queimadas, Rio Itapicuru, have normal 

 pectorals. 



Hyphessobrycon lutkeni (Boulenger), four specimens, 12, 16, 16, and 19 mm. 

 (without the caudal), Jacarehy (C. M. Cat. No. 2933), have archaic pectorals. 

 Three specimens, 19, 19, and 20 mm. (without the caudal), Jacarehy, (No. 2937), 

 have normal pectorals. The pectorals are also normal in thirteen hundred and 

 seventy-four specimens, 23 to 65 mm., from Rio Grande do Sul, Paraguay basin, 

 and the coastwise streams of southern Brazil. 



Hyphessobrycon bifasciatus Mrs. Elhs, twenty-seven specimens, 15-25 mm., 

 Cacequy (C. M. Cat. No. 2935); and five specimens, 18 to 27 mm., Munez Freire 

 (C. M. Cat. No. 2936), have archaic pectorals, while one hundred and eighty-four 

 specimens, 25 and 29 to 47 mm., from Campos, Sao Joao da Barra, Xiririca, Porto 

 Alegre, Morretes, Munez Freire, Lagoa Feia, and Cacequy have pectorals of the 

 adult type. 



Hasemania maxillaris Mrs. Ellis, one specimen, 29 mm., from Porto Uniao, 

 Rio Iguassu (C. M. Cat. No. 2937). 



Hasemania bilineatus Mrs. Ellis, four specimens, 14 to 16 mm., from Mogy das 

 Cruzes, Rio Tiet6 (C. M. Cat. No. 2938) have archaic fins; five specimens, 20 to 

 41 mm. (2939), from Mogy das Cruzes, Alto da Serra, Sao Paulo, have normal 

 pectorals. 



