def species_block(spc_dct):
    """ Writes the species block of the mechanism file

        :param spc_dct: dct containing the species data
        :type spc_dct: dct {spc_name:data}
        :return spc_str: str containing the species block
        :rtype: str
    """
    # Get the max species name length
    max_len = 0
    for spc_name in spc_dct.keys():
        if len(spc_name) > max_len:
            max_len = len(spc_name)

    buffer = 5

    # Write the spc_str
    spc_str = 'SPECIES \n\n'
    for spc_name, spc_data in spc_dct.items():
        spc_str += (
            '{0:<' + str(max_len+buffer) + 's}{1:>9s}{2:>9s}\n').format(
                spc_name, '! InChi: ', spc_data['inchi'])

    spc_str += '\nEND \n\n\n'

    return spc_str