                 If an error occurs on the call, `n' is undefined.
 
   plates         is a contiguous set of plates. The returned
                  plates are arranged in order of increasing plate
                  ID. The IDs of the returned plates range from

                     start

                  to

                     start + n - 1 

                  Each plate consists of three vertex indices. The
                  correspondence of elements of `plates' with the
                  elements of