New Mexico Ramshorn Snail (Pecosorbis kansasensis) is a freshwater snail ?that only occurs in the Pecos River Valley of Eddy County, New Mexico. They inhabit seasonal rock pools in limestone ledges that are protected from scouring by floods, but low enough to be filled with runoff from arroyos. They are considered a ?living fossil? because they are a species from the Pliocene that was thought to be extinct.