Origin of the bivalves
Diversification of bivalves
in substrate--ssoft shelled clams, quahogs,
on substrate--oysters, mussels
above substrate--scallops
Origin of the cephalopods
transformation from  passive  bottom dweller to passive floating predator to active swimming predator
Types of cephalopods
Orthocerids (Ordivician  straight  shelled  cephalopods