 Myriostoma is a fungal genus in the family Geastraceae . The genus is monotypic , containing the single species Myriostoma coliforme . It is an earthstar , so named because the spore @-@ bearing sack 's outer wall splits open into the shape of a star . The inedible fungus has a cosmopolitan distribution , and has been found in Africa , Asia , Europe , and North America .</s>