mailsystem module does not appear in the selection field for HTML Mail module class when I go to the mailsystem module configuration, only two selection fields appear

I do not know why this behavior can be given, there is some option that makes this disappear. I have installed the mailsystem and htmlmail modules

What I see in the site where the selection field is missing



What should be shown (what I need)
Below where you show in your screenshot, see the "New Class" field set. 
Expand that

For the Class to use for the format() (link is external) method field select HTMLMailSystem

Class to use for the mail() (link is external) method select SmtpMailSystem

Save the form. 

The new class will be available for use to set the Site Default.