Preheat the oven to 375 F (190 C) and line two large baking sheets with parchment paper. Squeeze the thawed spinach very dry so the triangles bake crisp.

In a large mixing bowl, combine the spinach, feta, ricotta, beaten eggs, green onions, dill, and nutmeg. Season lightly with salt and pepper.

Unroll the phyllo dough on a clean surface and cover it with a damp kitchen towel. Place one sheet on the work surface, brush lightly with melted butter, layer a second sheet on top, and brush again.

Slice the layered sheets lengthwise into 3-inch strips. Place a rounded tablespoon of filling at the bottom of each strip. Fold the corner over the filling to form a triangle, then continue folding like a flag.

Place the triangles seam-side down on the prepared baking sheets. Brush the tops with melted butter and bake for 20 to 25 minutes, or until deep golden brown and flaky.