Netherlands
Parasitic wasps known solely from the Netherlands include Aprostocetus epilobiellus (NHM - London), Camptoptera magna (NHM - London), and Echthroplexiella (or Ectroma) dunensis (fig. 2 at BHL). Other endemic insects include an ant Myrmica schenckioides (NEV pdf file), the freeloader fly Phyllomyza pallida (Milichiidae online), and an endemic genus of non-biting midge Molleriella calcarella (Nederlands Soortenregister).
A jellyfish Eucheilota flevensis (Marine Species) has only been recorded from the Netherlands.
Vascular plants known solely from the Netherlands include several brambles: Rubus canduliger (Stellaria)(SpringerLink), Rubus erinulus (IPNI), Rubus gloriosus (IPNI), Rubus nelliae (IPNI), and Rubus tubanticus (IPNI).
See also Aruba, Bonaire, Curaçao, Saba, Sint Eustatius, and Sint Maarten.