What is "physalus antiquorum"

Rorqual \Ror"qual\, n. [Norw. rorqualus a whale with folds.] (Zo["o]l.) A very large North Atlantic whalebone whale ( Physalus antiquorum, or Bal[ae]noptera physalus). It has a dorsal fin, and strong longitudinal folds on the throat and belly. Called also razorback.

Note: It is one of the largest of the whales, somethimes becoming nearly one hundred feet long, but it is more slender than the right whales, and is noted for its swiftness. The name is sometimes applied to other related species of finback whales.