226 Field Museum of Natural History — ZoOlogy, Vol. X. 



191 1, it rose from an elevation of 10 1.4 feet at 9:00 A. m. to no feet by 

 10:00 A. M. It is evident that at such times all boating on the river must 

 cease. 



The fish fauna in the upper courses of the Chagres is rather rich in 

 quantity but rather poor in variety. On the lower courses of the 

 Chagres the larger fishes have become comparatively rare, owing in 

 part at least to the illegal use of dynamite, but the nimiber of species is 

 greater than in the uninhabited region. 



The following is a list of species obtained by us in the Rio Chagres 

 Basin: Family SiluridcB; Pimelodella chagresi, Rhamdia wagneri: Family 

 LoricariidcB; Plecostomus plecostomus, Chcetostomus fischeri, Ancistrus 

 chagresi, Loricaria uracantha: Family Characidce; Astyanax ruherrimus, 

 Bryconamericus emperador, Brycon petrosus, Brycon chagrensis, Gephyro- 

 charax atricaudata, Creagrutus notropoides, Hyphessobrycon panamensis, 

 Pseudocheirodon affinis gen. et sp. nov., Compsura gorgona, Roehoides 

 guatemalensis, Piabucina panamensis, Hoplias microlepis: Family 

 Gymnotidee; Hypopomus brevirostris : Family Poeciliidce; Gambusia 

 cascajalensis, Gambusia episcopi, Gambusia nicaraguensis, Mollienisia 

 sphenops, Priapichthys tridentiger, Rivulus elegans: Family Mugilidce; 

 Agonostomus macracanihus, Agonostomus monticola, Joturus pichardi: 

 Family Cichlidce; jEquidens ccBruleopunctaius, Cichlasoma maculicauda, 

 Neetropolus panamensis, Geophagus crassilabris: Family Gobiidce; 

 Awaous taiasica, Dormitator maculatus, Leptophilypnus fluviatilis gen. 

 et sp. nov., Microeleotris mindii gen. et sp. nov., Eleotris isthmensis 

 sp. nov., Eleotris pisonis, Guavina guavina, Philypnus dormitor, and 

 Sicydium salvini. 



The representatives of the family Siluridce occur on both slopes of 

 Panama and southward and seem to be well established species that are 

 not at the present time undergoing any rapid changes in different 

 localities. 



Of the family LoricariidcB, Loricaria uracantha was taken only in the 

 Rio Chagres* and does in fact have no very near relatives. Since the 

 Isthmus of Panama is the northernmost limit of the range of this family 

 and its center of distribution occurs somewhere in South America, this 

 species may be regarded as one of the earliest migrants, t which appears 

 to have changed remarkably under the new environment. Chcetostomus 

 fischeri is really a Pacific slope fish in Panama, but it seems to have 

 reached this region before the last gap between the Rio Chagres and 

 the Pacific slope streams was closed. It has apparently not thrived 



*Loricaria uracantha is recorded from the Pacific slope of Panama, but it was 

 not seen there by us. 



fin our discussion on distribution, Panama is regarded as a very remote center 

 of distribution. See Meek, Field Mus. Nat. Hist. Pub., Zool. Ser., X, 1914, p. 134. 



