At present five species of Armadillidiidae, all belonging to the genus Armadillidium Brdt., are known from the Netherlands. These five species are Armadillidium vulgare (Latr.), A. nasutum B.-L., A. opacum (Koch), A. album Dollf., and A. pulchellum (Zenk.). The species will be dealt with in this order. Of every species, with the exception of A. vulgare, an enumeration is given here of the material present in the collection of the Rijksmuseum van Natuurlijke Historie at Leiden, the material collected in greenhouses excluded. Armadillidium (Armadillidium) vulgare (Latreille) This species, which is known also under the name Armadillidium cinereum (Zenk.), is the most common species of the genus from the Netherlands. It may be found throughout our country, and is often met in the neighbourhood of human settlements. It is therefore of no use to give here a list of the abundant Dutch material of this species present in the Rijksmuseum van Natuurlijke Historie at Leiden. Armadillidium (Pseudosphaerium) nasutum Budde-Lund Meerssen (southern part of the province Limburg); among Marchantia; June 10, 1927; leg. F. P. Koumans. — 24 specimens 4-11 mm. The specimens mentioned above were already reported upon by Koumans (1928), they are the only representatives of the species found up till now in the Netherlands in the open. The species is rather common in several Dutch greenhouses. Armadillidium nasutum occurs in Central and Northwest Italy, in Spain, in the western part of France, in Southern England and in the Netherlands; it attains in our country the northern limit of its range of distribution in the open.