Vaticanus A has been copied from Mediceus A, and Parisinus A from
Vaticanus A, so that they are practically one with their archetype.
Venetus A is of equal age and authority with Mediceus A. One can not
now get back of these two codices. There is none of remoter date for
Dio save the parchment Cod. Vat. 1288, containing most of Books
Seventy-eight and Seventy-nine,--a portion of the work for the moment
not under discussion. Coming to the second class, Mediceus B is a
joint product of copying from the two principal MSS. just mentioned.
In the third class, Parisinus B is a copy of Mediceus B with a little
at the opening taken from Mediceus A. This was the version selected as
a guide by Robert Estienne in the first important edition of Dio ever
published (A.D. 1548). All the rest, Escorialensis, Turinensis,
Vaticanus B, and Venetus B are mere offshoots of Parisinus B. The
Vesontinus codex is derived partly from Venetus A and partly from some
manuscript of the third class.

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 (Paléographie Universelle II, plate 7),