PETIOLES: 1–20 cm long, glabrous or sparsely appressed-hairy. LEAFLETS: 4– 17 mm long, broadly wedge-shaped, broadly rounded at the tips, symmetrically cuneate, sparsely pilose adaxially, moderately to densely pilose abaxially, the lateral margins straight or nearly so. SPOROCARPS: solitary, appearing somewhat nodding, produced from the tip of short peduncle attached at or rarely just above the petiole base, (2.4–)3–5 mm long, 2–3 mm wide, oblong-ovate in outline, the tooth distal to the stalk tip, absent or less commonly poorly developed, less than 0.2 mm long, bluntly triangular (Fig. 2C). MEGASPORES: 460–580 μm in diameter (excluding the apical papilla). MICROSPORES: 60–80 μm in diameter. 2n = 40. NOTES: Shallow water and margins of ponds, lakes, stock tanks, cienegas, and less commonly streams and marshy meadows: Coconino, Gila, Graham, Mohave, Navajo, Pima, Santa Cruz, Yavapai cos. (Fig. 1A); 1350–2250 m (4400–7400 ft); AZ, TX; s to Argentina. REFERENCES: Windham, M. D. and G. Yatskievych. 2009. Vascular Plants of Arizona: Marsileaceae. CANOTIA 5 (1): 30–33.