def augment_fix_sting(OrigFix, fix):
    """
    Adds a species to a psc file header.

    Parameters
    ----------
    OrigFix : str
        A psc file header
    fix : str
        Additional species to add to psc file header.

    Returns
    -------
    str
        A new psc file header that contains the contents of the original
        together with the new fixed species.
    """
    return OrigFix + ' %s' % fix