What is "natrix atra"

Black snake \Black" snake`\ (sn[=a]k) or Blacksnake \Black"snake\, n. (Zo["o]l.) A snake of a black color, of which two species are common in the United States, the Bascanium constrictor, or racer, sometimes six feet long, and the Scotophis Alleghaniensis, seven or eight feet long.

Note: The name is also applied to various other black serpents, as Natrix atra of Jamaica.