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ANNALS NEW YORK ACADEMY OF SCIENCES 



streams stand at high angles. This unstable condition seems to be due 

 to the elevation of the Andes during a late geological period. The heavy 

 rainfall, at times amounting to four or five inches within a few hours, 

 produces floods of immense volume. These go charging down the can- 

 yons with fearful fury, and at times it would appear that nothing could 

 withstand their sweeping energy. Yet these turbulent waters are the 

 habitat of fishes so wonderfully adapted to their surroundings that they 

 are able to grow and to multiply in great numbers. 



In external appearance they resemble the catfish or horned pout of the 

 north. The skin is smooth and scaleless. The color is a dark mottled 

 gray shading into a slightly yellowish tint on the posterior parts. They 

 rarely attain a length greater than twelve inches. As an article of food 



Fig. 1. — Arges marmoratus Regan ; side view 



they are esteemed by the natives and are well known by the local name 

 "Capitan." They have lately been described by C. Tate Began as Arges 

 marmoratus. 1 



Under usual conditions they are clumsy and awkward swimmers, wrig- 

 gling through the water like tadpoles, but as creepers and climbers they 

 are without rival in the fish family. The mouth is small, but is sur- 

 rounded by a broad, soft, rubber-like flap, very thin and flexible at the 

 edges (Fig. 2). It is a sucker mouth and the entire mechanism is so 

 perfectly adapted to the needs of the fish that it finds no difficulty in 

 firmly attaching itself to any convenient object. It is this ability to 

 make a quick anchorage that enables the fish to stay at home when nature 

 seems bent upon sweeping the canyons and water-courses clear of every- 

 thing movable. 



If, however, these fish were able only to keep themselves from being 

 washed out in flood times, they would be insufficiently equipped to main- 

 tain an existence in these mountain streams. If they depended upon 

 their imperfect swimming alone as a means of locomotion, whatever 

 migratory movement they attempted would inevitably have to be made 



1 Trans. Zoological Society of London, XVII, p. 314. 1904. 



