232 Field Museum of Natural History — Zoology, Vol. X. 



canensis, Lasiancistriis planiceps and Loricaria capetensis, all 

 originally described in one of our preliminary papers (1913), remain 

 peculiar to this stream. The last two, however, have very near relatives 

 on the Atlantic slope of Colombia. 



The families PygidiidcB and Cyclopidce are each represented by a 

 single species; both are described as new in our preHminary paper 

 (19 13). This in both instances represents the northernmost record for 

 these families. The Panama representatives have very near relatives 

 in Colombia. 



In the family CharacidcB there are the following species that appear 

 to be peculiar to the Rio Tuyra; Apareiodon dariensis, Creagrutus simus 

 and Hemihrycon dariensis sp. nov. While distinct, all have near 

 relatives in Colombia, and may therefore be regarded as among the 

 latest migrants. Phanagoniates macrolepis, Piabucina festcB and Hoplias 

 malabaricus do not occur in other streams of Panama, but their range 

 extends southward into Colombia or beyond. The rest of the repre- 

 sentatives of this family are found in other streams of Panama and 

 five of them occtir also in the Rio Chagres, viz.; Astyanax ruberrimus, 

 Bryconamericus emperador, Gephyrocharax atricaudata, Compsura gor- 

 goncs and Pseudocheirodon affinis gen. et sp. nov. Only the first one 

 of these is known from south of the Rio Tuyra. Br y con striatulus, 

 Brycon argenteus and Thoracocharax maculaius also appear to reach the 

 southern extreme of their range in the Rio Tuyra. They, however, 

 possess very near relatives in Colombia. The genus Brycon seems to 

 be yielding to the effects of different conditions, and now consists of 

 several rather closely related species. 



In the family Gymnoiidos, Sternarchus rostratus seems to be com- 

 mon to the Rio Tuyra and the Rio Atrato. Sternopygus dariensis sp. 

 nov. is limited to the Rio Tuyra Basin. The other two species are of 

 wide distribution. Eigenmannia virescens, however, is not known 

 north of the Rio Tuyra. 



The Poeciliidas are comparatively rare in this river basin and the 

 species are few. Mollienisia caucana reaches its northern limit of dis- 

 tribution in the Rio Tuyra; the variety Priapichthys trideniiger cana 

 seems to be peculiar to this stream; and Priapichthys dariensis is 

 known from this river basin and westward on the Pacific slope of 

 Panama. 



In the family Cichlidce there is a single species, Cichlasoma umbri- 

 ferunt, that seems to be peculiar to this stream. Cichlasoma tuyrense 

 and Cichlasoma calobrense are common to this stream and the Rio Ba- 

 yano. The other two species of this family are of rather wide distribu- 

 tion and occur on both slopes of Panama and southward. 



