Pluteus pusillulus Romagn. is the current name.
It was introduced as a replacement name for Pluteus minimus Romagn., Revue Mycol. (Paris) 2: 133 (1937) [MB#304668] which is a later homonym of P. minimus Henn. 1898 and therefore illegitimate.
Mycobank is updated accordingly.
See MB, IF.