Eurycarpum: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots  of Saskatchewan by V.L. Harms, A.L. Leighton and M.A. Vetter leading to this species. The answers are in the order you would normally work through the key.

Stigmas usually 2, occasionally 1 on some flowers; mature fruit bodies 5-10 mm long, obpyramidal, abruptly contracted to beaks, sessile, usually 2-locular and 2-seeded; inflorescences usually branched; leaves emergent; NOT [Stigmas 1; mature fruit bodies usually <5 mm long, ellipsoidal, fusiform or obovoid, tapering to beaks (+/- beakless in S. hyperboreum), stipitate or subsessile, 1-locular and 1-seeded; inflorescences branched or unbranched; leaves emergent or floating]