One night every week, a cohort of West Marin’s scarce 20 and 30-somethings gather in an office above the Old Western Saloon. The walls bear evidence of their twin focus on the land and the arts: a six-by-four foot United States Geological Survey map of the peninsula, shelves of poetry, literature and field guides, a poster of native California plants. The group plans to unite these passions in a forthcoming journal, the Inverness Almanac, which…