Elm oyster mushroom (Hypsizygus ulmarius), is a relatively rare mushroom variety.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/rare-mushroom-variety-holds-much-potential
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/hindu
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/agriculture
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/mushroom