Yacu-mama, a fabulous marine monster, said to haunt the lagoons of the Amazon, and to suck into its mouth and swallow whatever comes within a hundred yards of it; before bathing in a lagoon, where he apprehends its presence, the Indian sounds a horn, the effect of which is to make it reveal itself if it is there.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Yablonoi Mountains * Yahoo