The prehistoric vertebrate, the lancelet or Amphioxus.
"Lateral view of Amphioxus. The notochord runs from tip to tip. t., Tentacular cirri; G., reproductive…
"Amphioxus lanceolatus. A, ventral; B, side view of the entire animal. an, anus; atrp, atriopore; cd.…
The prehistoric chordate, the Ascidian or sea squirt.