I found an article on this so I thought I'd share my findings anyway....

In your PageType class add this to the declaration at the top of the class:

DefaultVisibleInMenu = false

So the code looks like this:

namespace codingexample.Templates.PageTypes
{
[PageType(
Filename = "/Templates/PageTemplates/EventArticle.aspx",
Name = "Event - Awards Event",
AvailableInEditMode = true,
DefaultVisibleInMenu = false,
Description = "Used to add Awards Event")]
public class EventArticleType : PageTypeBase
{
//YOUR CLASS CODE HERE
}