The limits and geographical position of these five districts (we are not entitled to call them provinces) have not yet been ascertained, though they have been often conjectured. It may be hoped that the discovery of further inscriptions may enable us to fix them decisively.[19] Besides these civil officers there were, according to the rearrangement of offices made by Diocletian, certain military commandants, called _comites_ and _duces_, of whom the count was, contrary to medieval usage, generally of higher rank than the duke. The _Notitia_ introduces us to three of these officers:-- 1. The Comes Britanniæ. 2. The Comes Litoris Saxonici per Britanniam. 3. The Dux Britanniarum. As to the first it gives us no information beyond the simple fact that the Provincia Britannia was “under his disposition”. The obvious conjecture is that numbers 2 and 3 were subject to him, but this is not asserted, and it perhaps militates against this theory that they, like him, belonged to the second grade in the official hierarchy, the _spectabiles_. It is possible that his special duty was the defence of Mid-Britain against the imperfectly subdued tribes of the Welsh mountains, and that the Second legion at Caerleon and the Twentieth at Chester were for a time under his orders for this purpose. The more interesting title for us is that of “The Count of the Saxon Shore in Britain”. He had under his command the garrisons of seven fortified places dotted around the eastern and south-eastern coast of England, from the Wash to Beachy Head.[20] He had also at his bidding the prefect of the Second “Augustan” legion, which had been moved from the quarters it had so long occupied at Caerleon-upon-Usk to Rutupiæ, or Richborough, close to the Isle of Thanet. The meaning of this arrangement is obvious. Like the Martello towers, which were reared along the same coasts last century, these fortresses were raised and garrisoned in order to defend that part of the projecting coast of Britain which was most exposed to the attacks of the Saxon pirates, already no doubt swarming in these seas in the fourth century, and to become far more formidable in the fifth century. The words, “per Britanniam,” added to the title of the _spectabilis comes_, are used because, as the _Notitia_ informs us, there was another Saxon shore which needed to be guarded on the other side of the channel; and, taken in this connexion, there is a special interest for us in the words of Apollinaris Sidonius, bishop of Clermont,[21] which show that in the succeeding century the coasts of Gaul, as well as of Britain, were kept in constant alarm by the Saxon sea-rovers.