Preheat oven to 350 degrees.
Cook pasta according to package directions to al dente. Drain.
Saute scallops until just cooked, they will continue to cook in oven. Set aside.
(If you didn't purchase cooked shrimp, cook them now being careful not to overcook.)
Melt butter in a large saucepan on medium heat. Add flour; stir with wire whisk until well blended.
Cook 2 minutes, gradually add milk, whisking as you pour to avoid lumps.
Bring to a boil on medium heat, stirring constantly. Reduce heat to low; simmer 3 to 5 minutes or until thick.
Remove from heat. Stir in Parmesan cheese and set aside.
Combine spinach cottage cheese, 2/3 cup mozzarella cheese and nutmeg.
Combine scallops, shrimp and crab in a different bowl.
Spread 1/4 of the cream sauce on the bottom of a 9x13 inch casserole dish.
Spread half the noodles over the sauce.
Spread half the seafood mixture over the sauce.
Spread half the spinach mixture over the seafood.
Top with remaining mozzarella cheese.
Cover with foil
Bake 25 minutes. Uncover and bake another 15 minutes or until bubbly and cheese is melted.
Let stand 5 to 10 minutes before serving.