Mnemosyne in Critias = Seshat in Manetho

[Danaus]

[108d] and encouragement, and in addition to the gods you mentioned I must call upon all the rest and especially upon Mnemosyne.1 For practically all the most important part of our speech depends upon this goddess; for if I can sufficiently remember and report the tale once told by the priests and brought hither by Solon, I am wellnigh convinced that I shall appear to the present audience to have fulfilled my task adequately. This, then, I must at once proceed to do, and procrastinate no longer.
...
[109e] to their descendants, concerning the mighty deeds and the laws of their predecessors they had no knowledge, save for some invariably obscure reports
Compare to:

https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Manetho/Introduction*.html
"Heliopolitan priest, Manetho (to quote from Laqueur, Pauly-Wissowa-Kroll, R.‑E. XIV., 1061) "was, without doubt, acquainted with  p. xii the sacred tree in the great Hall of Hêliopolis, — the tree on which the goddess Seshat, the Lady of Letters, the Mistress of the Library, wrote down with her own hand the names and deeds of the rulers.​11 He did nothing more than communicate to the Greek world what the goddess had noted down.​12 But he did so with a full sense of the superiority which relied on the sacred records of the Egyptians in opposition to Herodotus whom he was contradicting" (Fr. 43, § 73: Fr. 88). His native town, Sebennytus, was visited as a place of learning by Solon when Ethêmôn was a priest in residence there (see Proclus in Plat. Tim. I.101, 22, Diehl); and the Greek culture of the place must have been a formative influence upon Manetho at an early age. "