The author examined a series of Patellas, present in the collections of the ”Committee on the Netherlands’ Marine Flora and Fauna”, deposited in the Rijksmuseum van Natuurlijke Historie at Leiden. He arrived at the conclusion that there are three species of Patella to be found in the Netherlands, viz., Patella vulgata L., P. athletica Bean, and P. depressa Penn. All specimens found in autochthonous localities proved to be P. vulgata. As to the adventives there must be distinguished between the specimens transported to the Dutch coast by Fucus species and those transported by Himanthalia elongata (L.) Setchell. The former belong without exception to P. vulgata, the latter for the smaller part to P. athletica, for the greater part to P. depressa. A description of the three species, mainly based on Dutch material, is given.