How do I exclude a base class using fluent mappings in Fluent NHibernate?

Question

I have an abstract base class, Entity, that all my POCOs derive from:

public abstract class Entity
{
    public virtual Guid Id { get; set; }
}

And the mapping file:

public class EntityMap<T> : ClassMap<T> where T : Entity
{
    public EntityMap
    {
        Id(x => x.Id);
    }
}

This way, I don't have to write Id(x => x.Id) in every mapping file by using this:

public class Something : EntityMap<T>
{
    blahblah
}

I'm auto-generating my database schema, and everything looks fine, except that the Entity base class is added as a table. Using fluent mappings, how do I configure it so that the Entity class is excluded from the database schema?