Saltmarsh coffeebean snails (Melampus bidentatus) are grazers of standing-decaying cordgrass, just as are saltmarsh periwinkles , but they apparently don't take fungal material so intensively that they cause reductions in fungal productivity like the periwinkles can. Coffeebean grazing actually stimulates fungal growth (Graça, Newell & Kneib, 2000, Mar. Biol. 136:281-289). Coffeebean snails are most obvious at the upland edges of smooth-cordgrass marshes, but I have found small ones deep in the marsh, and they generally hide during the day, so they may be more widely distributed than is now generally thought. Coffeebean snails eat all sorts of marsh-edge plant litter (marshgrass, oak leaves, palm fronds, etc.) but they like standing-decaying cordgrass just fine. I have raised them from 2-mm babies to full adult size (13-mm shell length) on standing-decaying cordgrass as the only food. See Newell & Porter, 2000, pp. 159-185 in Weinstein & Kreeger, Concepts and Controversies in Tidal Marsh Ecology, Kluwer.