Hippopodes
Pliny the Elder's "Natural History" locates this island near the Scythian coast; Pomponius Mela's "De situ orbis" places it in or around the North Sea , mentioning it alongside Denmark and the Orkney Islands ( Mela iii . 
<triplet> Pliny the Elder <subj> Natural History <obj> notable work <triplet> Natural History <subj> Pliny the Elder <obj> author <triplet> Orkney Islands <subj> North Sea <obj> located in or next to body of water