The genus Calypogeia essentially has the characteristics of the family (description in the moment only in german), which vice versa essentially consists of this genus. In europe it is represented by about 10 species. The distinguishing characteristics between those are the shapes of the leaves and the leaf cells.
Calypogeia muelleriana has obtuse oval, at most very little acuminate or bilobed leaves. The underleaves are divided into two lobes for about 1/3 of their length. In the corner of the leaf cells there are no triangular corner thickenings, as it is the case in the other species of the genus (and as can be seen on the picture of Nardia scalaris). The cells contain about 3-8 oil bodies.
The plants of this species mostly grow on humid, loamy places, sometime also on humus or on rotten wood. It is a not very noticeable, but in the flatlands rather common species. It can be found on the whole northern hemisphere, even far in the north, mostly in the lower regions.