This article is describing the gnosiological understanding of a social myth instead of the classical myth ontology. This understanding of a social myth as conditionally true statements which is proved by the system analysis of context and by axiology is caused by utility.An object which illustrates the state of this article is the moment displaying a social myth concerning a bird the Stormy Petrel (Procellariidae.) It is the protagonist of «Song of a Storm Petrel» written by great Russian author A.M.Gorkogy and a base revolutionary, mythopoetic image of the USSR. The Stormy Petrel «as a streak of black lightning» is imperatively acquired truth for the Soviet man. Destruction of a social myth of the Stormy Petrel is objectively caused by distinctions of appearance and habits of representatives of bloodline of these birds which live in territory of the USSR and carry the name "Fulmar" (Fulmarus glacialis) which means silly person and, the so-called, small petrel (Procellariidae puffinus) which caries the name of the snake "Python" and inhabits in the Mediterranean where A.M.Gorky has lived. This demystification of semiotics of a totalitarian mode of the USSR, given as an example of the basic material, is the largest discovery in this area in the 21 century.