230 Field Museum of Natural History — Zo6logy, Vol. X. 



to our present knowledge there is not a single species whose habitat is 

 limited to this river basin alone, as all species occurring here are fovmd 

 also in streams either to the eastward or westward of it. 



The Rio Tuyra and Its Fauna. 



This river like the Bayano is subject to the high tides of the Pacific 

 coast. It empties into San Miguel Bay, and for many miles inland it is 

 a broad expanse of water in which the current changes twice daily. 

 The head of steam boat navigation is at El Real about 75 miles above its 

 mouth. The head of tide is at Pinogana about 15 miles above El Real. 



Several miles below El Real is the mouth of the Rio Chucimaque, 

 a tributary nearly as large as the main stream. This stream lies almost 

 wholly within the San Bias region. Its exploration was therefore not 

 undertaken. 



The main stream was followed as far as Boca de Cupe, about 30 

 miles above the head of steamboat navigation. This distance was 

 traveled in the native wooden dug-out. This stream has rather swift 

 current above the head of tide, but there are no strong rapids, such as 

 occur in the Rio Chagres. Before reaching Boca de Cupe the mouths of 

 three tributaries of rather large size are reached, namely the Rio Aruza, 

 Rio Yape, and the Rio Capeti. An overland trip from Boca de Cupe 

 was made to the upper part of the Aruza, and the other two were fol- 

 lowed only a short distance above their mouths. Interesting collections 

 were obtained from each. At the native village of Boca de Cupe, 

 located at the mouth of the Rio Cupe, the main stream was fished as 

 well as the smaller tributary. 



From Boca de Cupe the Darien Gold Mining Company has con- 

 structed a small tramway to its mines in the mountains at Cana, a 

 distance of about 30 miles. This was followed and some of the small 

 streams en route were fished. At Cana the small Rio Cana and the 

 somewhat larger Rio Setiganti were visited and rather extensive col- 

 lections made in each. An overland trip of about 10 miles was made 

 from Cana to the Rio Grande another one of the upper tributaries of 

 the Rio Tuyra. These small mountain streams are all very rocky and 

 collecting is difficult. Most of the streams were clear and cool at the 

 time of our visit, but the Rio Cana was very turbid with a reddish sedi- 

 ment on its bed. However, a number of very interesting forms not 

 seen elsewhere were secured from the latter. 



Some of the upper tributaries of the Rio Tuyra and those of the Rio 

 Atrato of the Atlantic slope of Colombia come very close together and 

 the water shed between the two basins is very low. We were informed 

 by the employees of the Darien Gold Mining Company that the Indians 



