The Featured Fossil: Exogyra
Exogyrae were bivalves closely related to oysters. Like oysters (Ostrea), Exogyra was a Pteriomorph, meaning that it cemented itself to something or rested on the bottom. Unlike oysters it did not live in closely packed beds, but spread out on the sea floor. The other type of bivalve, known as Heteodonts, did not cement themselves to objects but burrowed into the mud.
Because the left side of the shell grew faster than the right, Exogyra's thick shell curved clockwise producing a spiral pattern.
Maryland's State Fossil
Ecphora gardnerae gardnerae is one of the more elegant fossil shells you can find in the Miocene deposits of Calvert Cliffs. It is also the official Maryland state fossil.
Ecphora gardnerae was a small snail that was first described in 1770 in the scientific publication Historiae Conchyliorum by Martin Lister. Ecphora gardnerae was originally thought to the same species as Ecphora quadricostata. In 1984, The Maryland State Assembly passed a resolution declaring Ecphora quadricostata the state fossil of Maryland. However the two snails were later declared to be separate species, so in October 1994, the State Assembly passed Chapter 688, Section 13-311 which declared Ecphora gardnerae to be the State fossil.