In a large bowl, combine spinach, shrimp, scallops, crab meat, ricotta cheese, garlic & salt & pepper. Fill pasta shells. Spread some sauce in the bottom of a 9 x 13-inch baking pan. Lay filled shells single file in pan. Pour remaining sauce over all & top with a sprinkling of parmesan. Bake 20-30 minutes, until the cheese becomes a little brown.