It is said truly that the Ammonite, Orthoceras, and Nautilus of these ancient rocks were of the tetrabranchiate division, and none of them so highly organised as the Belemnite and other dibranchiate cephalopods which afterwards appeared, and some of which now flourish in our seas.    From Wordnik.com.  [The Antiquity of Man] Reference

Gasteropoda, Heteropoda, Pteropoda, and dibranchiate Cephalopoda.    From Wordnik.com.  [Journal of the Proceedings of the Linnean Society - Vol. 3 Zoology] Reference