Note 77 — Chapter II · THE SANCTUARIES IN THE CITADEL.
Reading edition
Only once so far as I know is Kekrops definitely called a snake, in the Hekale of Callimachus; speaking of the decision in favour of Athene as against Poseidon he says (V. 9)
τήν ῥα νέον ψήφῳ (τ)ε Διὸς δύο καὶ δέκα τ’ ἄλλων ἀθανάτων ὄφιός τε κατέλλαβε μαρτυρίῃσιν.
See Gomperz, Rainer Papyrus VI. 1897, p. 9.