“greater tooth moss”
How to recognize Plagiomnium medium: This moss resembles other species of Plagiomnium in growth habit and has 1-2 celled sharp teeth all around the leaf with long-decurrencies or leaf extensions growing down the stem from the leaf base. Since it has both male and female organs on the same plant it is usually fertile and has several seta growing from each plant; Plagiomnium cuspidatum has only a single seta and capsule per plant. If it has no capsules it might be confused with Plagiomnium ellipticum, but that plant has very blunt teeth and has no decurencies.
Where to find Plagiomnium medium: Look for this moss on humus in wet places along streams.