The Marauder's Map & Pettigrew

[bootekusic]

No: HPFGUIDX 45033

Ok, first off, I am new here so I apologize if this has been brought 
up before. 

Heres the issue, the Marauder's Map is introduced in chapter 10 of 
POA. Wouldn't Harry have seen Peter Pettigrew's name on it? We know 
that Animagi show up on the map because Prof. Lupin said he saw 
Pettigrew's name on it. If he had been checking on it before why 
hadn't he seen Pettigrew's name before that? Is this a valid question 
or am I just confused?

 - Bootekusic