Dictionary.net

• Below the notochord.

1920 - A dictionary of scientific terms.
By Henderson, I. F.; Henderson, W. D.

• [Greek] Below the notochord; appl. lower lobe of caudal fin; appl. bar of mesodermal tissue developing into ventral arch of atlas and amalgamating with fibrocartilages in other cervical vertebrae.

1920 - A dictionary of scientific terms (6th edition)
By J.H. Kenneth