A second hand book I bought recently La Pampa, Grafías y etimologías toponímicas aborígenes by Alberto Vuletín (1972) , has an interesting reference regarding hairy snakes.
The book explains the origin of the name places in the Province of La Pampa and focuses on those of native origin. Though La Pampa is officially part of the Patagonia region, (having joined the Patagonian Provinces) the historical northern boundary of that region has been set along the Colorado River, which also marks La Pampa's southern frontier. So, if I were a purist, I would not mention this as a Patagonian creature, but as the natives that peopled the area also lived in Patagonia, I will included in the blog.
Its author includes a map by Alvaro Barros, drawn in 1872, a few years before the Argentine government undertook a military campaign (1878-1884) to occupy the region and snatch it from the native's hands. Interestingly, it mentions a Calchochá or "Snake with hairs" ("Víbora con pelo" in the Spanish original), close to the border between the provinces of La Pampa and Buenos Aires.
It is just north of a place named "Agua fria dulce" (cold freshwater) which, in the native language was known as "Atreucó" (from Athé = cold, có = water or uúvco = spring) which is set close to the provincial highway number 18 (37°07'S, 63°48'W).
There are several lakes in that region, but none of them bear nowadays the name of "hairy snake".
In a post nearly one year ago, on the "Patagonian" Hairy Snake, I included a comment by a military commander along the Pampa frontier Federico Barbará, who mentioned a lake named precisely "hairy snake", perhaps it was the same lake mentioned above.
The book has some other interesting things, I will mention them in my next post (the Chueiquehuecu monster).
By the way, Alvaro Barros was the first Governor of Patagonia Territory (1878-1882), so it may be correct to include the Pampean hairy snake as part of Patagonia's mythical fauna.
 Alberto Vuletín, (1972). La Pampa, Grafías y etimologías toponímicas aborígenes. B. Aires, Eudeba.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia2010 International Year of Biodiversity Copyright 2009-2010 by Austin Whittall ©