 <td align="right">C15</td>   <td align="right">1</td> <td align="right">2</td> </tr>
  
  <tr> <th colspan="4" class="ftype">Mailles tétragonales</th> </tr>
  <tr> <th align="left">Tétragonal simple</th>         <td align="right">st</td>    <td align="right">2 (a et c)</td> <td align="right">1</td> </tr>
  <tr> <th align="left">Tétragonal centré</th>  <td align="right">bct</td>   <td align="right">2 (a et c)</td> <td align="right">1 ou 2</td> </tr>
  <tr> <th align="left">Tétragonal faces centrées ou