Although my two favorite plant books, Botanica and Passalong Plants, both call this flower a snowflake, I have difficulty with the name.
Sure, this picture shows a white flower, but it really looks like a bell. And it has a blue identically shaped friend nearby in the garden.
Its first name is Leucojum, and its other name is probably aestivum. This flower appears in early spring, usually in small clumps scattered throughout the yard.
It definitely is a passalong plant. Often it seems to travel to the garden with another flower with a larger bulb, and, if asked, the gardener cannot tell where this very welcome flower came from.