Malacopterygi or Malacopterygii: How To spell?

The word Malacopterygi is misspelled against Malacopterygii, a noun meaning "An order of fishes in which the fin rays, except the anterior ray of the pectoral and dorsal fins, are closely jointed, and not spiny. It includes the carp, pike, salmon, shad, etc. Called also Malacopteri."