Assuming the PTR RRs are accurate, that would appear to be true:

  $ traceroute 128.31.0.39
  ...
  15  mitnet.trantor.csail.mit.edu (18.4.7.65)  40.218 ms  40.661 ms  40.900 ms
  16  asperta.helicon.csail.mit.edu (128.30.0.246)  45.345 ms  47.082 ms *
  17  belegost.csail.mit.edu (128.31.0.39)  44.074 ms !X  45.023 ms !X  45.549 ms !X