The Mollusks
Phylum Mollusca
- Class Polyplacophora: chitonsmarine, 8 overlapping calcareous plates
- Class Gastropoda: snails and slugs originally with shell, but some have lost shell during evolution; head /w tentacles and eyes
- Class Bivalvia: mussels, clams, scallops, oysters two lateral shells (valves), hinged dorsally, no head
- Class Cephalopoda: squid, octopuses, nautilushighly-developed nervous system, complex lens eyes, intelligence and learning abilities