def split_column(col, species):
    """
    Split the column name of the form 'species/name'
    """
    fields = col.split('/')
    if len(fields) != 2:
        msg = "new column names should be prefixed by 'species/' where "
        msg += "'species' is one of %s" % str(species)
        raise ValueError(msg)
    this_species, subcol = fields
    if this_species not in species:
        args = this_species, str(species)
        raise ValueError("species '%s' is not valid; should be one of %s" %
            args)
    return this_species, subcol
