The parchment manuscript to which allusion was made above is only some three centuries later than the time of Dio himself.  It covers the ground from Book 78, 2, 2, to 79, 8, 3 inclusive (ordinary division).  It belonged to Orsini, and after his death (A.D. 1600) became the property of the Vatican Library.  It is square in shape and consists of thirteen leaves, each containing three columns of uncials.  In spite of its age it is fairly overflowing with errors of every sort, many of which have been emended by an unknown corrector who also wrote in uncials; this same corrector would appear to have added the last leaf.  And there are a few additions in minuscules by a still later hand.  The leaves are very thin and in some places the ink has completely faded, showing only the impression of the pen.  For specimen illustrations of this codex see Silvestre (Paleographie Universelle II, plate 7), Tischendorf (cod.  Sinait. plate 20) and Boissevain’s Cassius Dio (Vol.  III).

The dates of these codices (centuries indicated by Arabic numerals) are about as follows: 

I. Mediceus A-Ma-          (11)
I. Venetus A-Va-           (11)
I. Vaticanus A             (15)
I. Parisinus A             (17)
II.  Mediceus B              (15)
III.  Parisinus B             (15)
III.  Venetus B               (15)
III.  Vaticanus B             (15)
I. and III.  Vesontinus              (15)
III.  Turinensis              (16)
III.  Escorialensis            (?)
I. Codex Vaticanus graecus No. 1288 (5-6).

Mediceus A contains practically Books Thirty-six to Fifty-four, and Venetus A Books Forty-one to Sixty (two “decades").  As they are both the oldest copies extant and the sources of all the others, modern editors would confine themselves to them exclusively but for the fact that in each some gaps are found.  In Mediceus A, for instance, two quaternions (sixteen leaves) are lacking at the start, Leaf 7 is gone from the third quaternion, Leaves 1 and 8 from the fourth; from the thirty-first (now Quaternion 29) Leaf 1 has been cut, from the thirty-third and last Leaf 5 has disappeared.  Likewise in Venetus A there are some gaps, especially near the end, in Book Sixty, where three leaves are missing.  Hence (without stopping to take up gaps and breaks in detail) it may be said that the general plan pursued at the present day is to adopt a reading drawn for each book from the following sources respectively: 

Book 36.  Mediceus A, with lacuna of chapters
                  3-19 incl., supplied by the
                  mutual corrections of Vaticanus
                  A and Parisinus B.

Books 37 to 49.  Mediceus A.

Books 50 to 54.  Vaticanus A (vice Mediceus A).

Books 55 to 59.  Venetus A.

Book 60.  Venetus A, except chapter 17, sections
                  7 to 20, and chapter 22,
                  section 3, to chapter 26, section
                  2,—­two passages supplied by
                  Mediceus B.