I have been trading using Wi-fi to get Pokemon for my Heart Gold game. Today I noticed something odd about the list of Pokemon that I could trade. This was when I was both Seeking and looking to trade the Pokemon I have Deposited. Certain Pokemon were not on the list, while their final evolved stages were. I wanted to get a Bagon or Shelgon, but neither name was on the list. Although their final evolved form, Salamence, was on the list. Is there any particular reason for this?