Lucan [1st century CE] (Pharsalia, book 9, verse 800): ...natrix who in bubbling fount / Fuses his venom. - [Ridley, 1919 translation]

Isidore of Seville [7th century CE] (Etymologies, Book 12, 4:25): The natrix is a snake that contaminates water with its poison. Whatever spring it was in, it would mix its poison into it. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Serpents 8.24): The natrix is a serpent, as Isidore says, that infects the water with its poison. For it mixes its poison in the water of whatever spring it is in. Hence Lucan: And the natrix is the violator of water. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book18.9): Also Natrix is an adder, and hath that name, for he infecteth with venim each well that he commeth nigh, as Lucan sayth, and saith Natrix infecteth waters, as Isidore sayth libro. 7. - [Batman]