228 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



ward to Guatemala. Neetroplus panamensis is known only from the 

 Rio Chagres, although there are representatives of the genus in Costa 

 Rica and other parts of Central America. The last two species may 

 be regarded as migrants from Central America. 



The fresh and brackish water representatives of the family Gobiidce 

 alone seem to have Panama as a center of distribution. They appear 

 to have yielded to the different environment of the two slopes and 

 only one species, Sicydium salvini, an upland form, is now common to 

 both slopes. Aivaous taiasica, Dormitator maculatus, Microeleotris 

 mindii sp. nov., Eleotris pisonis and Philypnus dormitor all have very 

 near relatives on the Pacific slope, differing sufficiently so that 

 usually they can be distinguished quite readily. 



THE Rio BAYANO AND ITS FAUNA. 



The Rio Bayano is a broad stream at its mouth and owing to the 

 excessively high tides on the Pacific coast of Panama, varying from 

 20 to 30 feet between high and low water, the current changes twice 

 daily for 30 or more miles up stream. Throughout this entire distance 

 the river is broad and muddy, but the head of steam boat navigation is 

 not far above the mouth of the Rio Mamoni which empties into the 

 main stream about 20 miles from the sea. The lower course of the 

 Bayano has large quiet bays where the crocodile is very abundant. 

 There are places where on a sunny day an observer may stand in one 

 position and count a hundred or more noses of these beasts projecting 

 above the water. Many marine species of fishes run up and down the 

 lower part of this stream with the tides. 



The Rio Mamoni has a much greater fall than the main stream and 

 soon rises above tide level. It then becomes, at least during the dry 

 season, a clear stream with a rocky or pebbly bottom. About 10 or 

 15 miles above its mouth is situated the town of Chepo which is one of 

 the oldest and best known towns of Panama outside of the limits of the 

 Canal Zone. During the dry season this stream is quite small at this 

 village. It was so low during our visit that we were obliged, in order 

 to reach Chepo, to leave our dug-out behind and travel overland the 

 last 5 or 6 miles. In this region of savanas this was not difficult. We 

 did not explore the stream beyond Chepo, although it extends for many 

 miles back into the mountains, and very probably supports forms of 

 fishes not obtained by us. 



Following again the course of the main stream for from 10 to 15 

 miles above the mouth of the Mamoni another tributary of considerable 

 size is reached. This is the Rio Calobre which flows through a densely 

 wooded and uninhabited region. The lower portion of this stream is 



