Best way to get runtime Type of T?

Given the example code below, I'd like to get the runtime type of T inside a generic method (in this case retrieveData). When I create an XMLFilePersisting I use the interface, namely ITransferable rather than the implementing Types since in my client I want to have a list of all of them together:

List<XMLFilePersisting<ITransferable>> allThem;

So if in retrieveData I do typeof(T) that should return ITransferable which doesn't give me enough info to load the items from the file. The only way I could figure out how to do this was by passing an instance of the implementor of ITransferable in the constructor, but this kind of feels like there should be a better way. Suggestions?

public interface IPersisting<T> {
        List<T> retrieveData();
        bool persistData(List<T> lst);
    }

public interface ITransferable {
    Type getRuntimeType();
}

public class XMLFilePersisting<T> : IPersisting<T> where T : ITransferable {
    private readonly T defaultT;
    //...
    public XMLFilePersisting(string thefile, string thepath, T def) {
        //...
        defaultT = def;
    }
    ...

    public List<T> retrieveData() {
      List<T> retVal = new List<T>();
      Type runType = defaultT.getRuntimeType();
      string elemName = runType.Name;
      using (FileStream fs = new FileStream(FQ_FILE_PATH, FileMode.Open, FileAccess.Read)) {
        using (XmlReader reader = XmlReader.Create(fs)) {
           //below line won't work, typeof resolves at compileTime      
           //XmlSerializer xmlSer = new XmlSerializer(typeof(T));
           XmlSerializer xmlSer = new XmlSerializer(runType);
           if (reader.ReadToFollowing(elemName)) { //go to the first test, skipping over ListofT
              do {
                 T testVal = (T)xmlSer.Deserialize(reader);
                 retVal.Add(testVal);
                }
              while (reader.ReadToNextSibling(elemName));
           }
         } //end using xmlreader
      } //end using FileStream
    return retVal;
  } //end retrieveData
} //end class XMLFilePersisting

Additional info:

Client code looks like below. As you can see I need all

IPersisting<ITransferable>

instances, but the problem is in retrieveData, that makes typeof(T) = ITransferable which doesn't give me enough info to do the deserialization. That is why I pass concrete implmentations of ITransferable to the constructor (MyClass1, MyClass2). This seems to work, but feels like a hack.

IPersisting<ITransferable> xfpMC1 = new XMLFilePersisting<ITransferable>("persistedMC1.xml", myTempDirectory, new MyClass1());
IPersisting<ITransferable> xfpMC2 = new XMLFilePersisting<ITransferable>("persistedMC2.xml", myTempDirectory, new MyClass2());

A