Otidea onotica (Pers.) Fuckel is a small, yellow cup fungus found often near packed-down paths in forests, originally thought to be in the genus Peziza. Characteristically, these cups have a split down one side, lending the characteristic to it’s common names of “rabbit’s ear fungus” and “lemon peel fungus” (Fig 1). The cups are usually small, often ~5 cm tall and ~3 cm across, with a smooth interior surface and a slightly rough exterior, often spreading into multiple cups per fruiting body or a wide-spread, more open cup (Fig. 2). O. onotica is common in forests, hardwood and pine, in Europe and North America (Fig. 3). It is saprotrophic, growing in clusters or scattered under trees. Inside the cup, ascospores are produced in sets of 8 in the asci, which can then be easily spread from the cup. Spores are ellipsoid and smooth, about 12 um long, and often contain two visible oil droplets, and the spore print is reported to be white. Some sources report O. onotica as being edible, but most agree that they are inedible or possibly have some medicinal value.
Mushrooms of the Midwest by Michael Kuo and Andrew S. Methven