But, it will be asked, how do we know that Aldus used Π rather than some other manuscript that had a very similar text and that happened to have gone through the same travels? To answer this question we must examine the relation of Π to the other extant manuscripts in the light of what is known of the transmission of Pliny’s _Letters_ in the Middle Ages. A convenient summary is given by Merrill on the basis of his abundant researches.[19] [Footnote 19: _C.P._ X (1915), pp. 8 ff. A classified list of the manuscripts of the _Letters_ is given by Miss Dora Johnson in _C.P._ VII (1912), pp. 66 ff.] [Sidenote: _Classes of the manuscripts_] Manuscripts of the _Letters_ may be divided into three classes, distinguished by the number of books that each contains. Class I, the ten-book family, consists of _B_ (Bellovacensis or Riccardianus), now Ashburnhamensis, R 98 in the Laurentian Library in Florence, its former home, whence it had been diverted on an interesting pilgrimage by the noted book-thief Libri. This manuscript is attributed to the tenth century by Merrill, and by Chatelain in his description of the book. But Chatelain labels his facsimile page “_Saec._ IX.”[20] The latter seems the more probable date. The free use of a flat-topped _a_, along with the general appearance of the script, reminds me of the style in vogue at Fleury and its environs about the middle of the ninth century. A good specimen is accessible in a codex of St. Hilary on the Psalms (Vaticanus Reginensis 95), written at Micy between 846 and 859, of which a page is reproduced by Ehrle and Liebaert.[21] _F_ (Florentinus), the other important representative of this class, is also in the Laurentian Library (S. Marco 284). The date assigned to it seems also too late. It is apparently as early as the tenth century, and also has some of the characteristics of the script of Fleury; it is French work, at any rate. Keil’s suggestion[22] that it may be the book mentioned as _liber epistolarum Gaii Plinii_ in a tenth-century catalogue of the manuscripts at Lorsch may be perfectly correct; though not written at Lorsch, it might have been presented to the monastery by that time.[23] These two manuscripts agree in containing, by the first hand, only Books I-V, vi (_F_ having all and _B_ only a part of the sixth letter). However, as the initial title in _B_ is PLINI · SECUNDI · EPISTULARUM · LIBRI · DECEM, we may infer that some ancestor, if not the immediate ancestor, of _B_ and _F_ had all ten books.