64 Field Columbian Museum — Zoologv, Vol. III. 



from Mr. Woodside, custom agent for the Mexica.n Central Railroad 

 at Cuidad Juarez. 



The following River systems were examined as listed below: 



The Casas Grandes System. 



The Rio Casas Grandes is a small mountain stream which 

 flows into Lago de Guzman. In the dry season the lake becomes 

 nearly or entirely dry and there is very little water in the river 

 below Terrasas. At Colonia Juarez, about 16 miles above Ter- 

 rasas, the river the last of June contained little water, nearly 

 all of which was taken out a short distance below into irriga- 

 ting ditches. The fish life was abundant, but there were only 

 a few species. The water was clear, and cooler than other similar 

 mountain streams farther south. Where the water was confined 

 in holes and not running it contained a large amount of algae, 

 enough to fill the meshes of our net and make hauling difficult. 

 Lago de Guzman at the time of our visit was dry. A few fishes 

 were taken from a small spring branch near the railroad station. 

 It is probable that this river system was once a tributary of the 

 Rio Grande. 



The Santa Maria System. 



The Rio Santa Maria runs parallel to the Rio Casas Grandes 

 and empties into Lago de Santa Maria about 10 miles southeast 

 of Guzman. These lakes are separated by a comparatively low 

 ridge, but so high that their Avaters have not mingled wuth each 

 other for a considerable time. I visited this water system only 

 at Santa Maria. The lake was dry, but there were several large 

 ponds fed by many large springs. These ponds were surrounded 

 by a considerable amount of aquatic vegetation. The bottoms 

 were of loose mud or muck. The water in the springs and 

 spring brooks was clear, and contained C. elegans and N. lutrcnsis 

 in abundance. • 



The Carmen System. 



The Rio Carmen is a small river east of the Rio Santa Maria. 

 It empties into Lago de Patos about 50 miles southeast of 

 Lago de Santa Maria. At the time of my visit, June 21, the lake 

 was dry except a few holes some 20 feet wide and 50 or 60 feet in 

 length. These were reported to contain fish, but a half day's 

 seining resulted in getting none. At the San Jose Ranch, some 



