What is ground red pepper? I have the 75th anniversary edition of Joy of Cooking. I've now come across two recipes that call for "ground red pepper" (enchiladas and a dry rub). I've never heard of ground red pepper before and cannot find it at the store. 

Is it ground red bell pepper or something hot like cayenne? What should I use as a substitute?
In most instances I've seen, in American cookbooks, "red pepper" refers to cayenne pepper or chili powder (not the spice mix designed for making chili con carne, but dried, ground chilis). It is usually spicy rather than being red bell pepper. 

Edit to add: I'm talking about this type of product:


McCormic Ground red pepper


Source