A. 4.--His reign and that of his successor (and murderer) Allectus are marked by the last and most extraordinary development of Romano-British coinage. Since the time of Caracalla no coins which can be definitely proved to deserve this name are found; but now, in less than ten years, our mints struck no fewer than five hundred several issues, all of different types. Nearly all are of bronze, with the radiated head of the Emperor on the obverse, and on the reverse devices of every imaginable kind. The British Lion once more figures, as in the days of Cymbeline; and we have also the Roman Wolf, the Sea-horse, the Cow (as a symbol of Prosperity), Plenty, Peace, Victory, Prudence, Health, Safety, Might, Good Luck, Glory, all symbolized in various ways. But the favourite type of all is the British warship; for now Britannia, for the first time, ruled the waves, and was, indeed, so entirely Mistress of the Sea that her fleet appeared even in Mediterranean waters.[322] The vessels figured are invariably not Saxon "keels," but classical galleys, with their rams and outboard rowing galleries, and are always represented as cleared for action (when the great mainsail and its yard were left on shore). A. 5.--The usurpation of Carausius, "the pirate," as the Imperial panegyrists called him,[323] brought Diocletian's great reform of the Roman administration within the scope of practical politics in Britain. The old system of Provinces, some Imperial, some Senatorial, with each Pro-praetor or Pro-consul responsible only and immediately to the central government at Rome, had obviously become outgrown. And the Provinces themselves were much too large. Diocletian accordingly began by dividing the Empire into four "Prefectures," two in the east and two in the west. Each pair was to be under one of the co-Augusti, who again was to entrust one of his Prefectures to the "Caesar"[324] or heir-apparent of his choice. Thus Diocletian held the East, while Galerius, his "Caesar," took the Prefecture of Illyricum. His colleague Maximian, as Augustus of the West, ruled in Italy; and the remaining Prefecture, that of "the Gauls," fell to the Western Caesar, Constantius Chlorus. Each Prefecture, again, was divided into "Dioceses" (that of Constantius containing those of Britain, Gaul, Spain, and Mauretania), each under a "Vicar," and comprising a certain number of "Provinces" (that of Britain having four). Thus a regular hierarchy with rank above rank of responsibility was established, and so firmly that Diocletian's system lasted (so far as provincial government was concerned) till the very latest days of the Roman dominion.