New Castle County

Insects and Crustaceans: Phylum Arthropoda

Arthropods are animals with a segmented body, external skeleton, and jointed appendages. The Arthropoda includes insects and crustaceans. Only two groups of arthropods are common as fossils in the Cretaceous of the C&D Canal area, and both are types of crustaceans: the Malacostraca (crabs, lobsters, and shrimp) and the microscopic Ostracoda.

Segmented Worms: Phylum Annelida

Annelids are segmented worms. The remains of the soft-bodied segmented worms are not usually preserved as fossils. Some marine (salt-water) types, however, secrete tubes of calcium carbonate to use both as a home and to provide protection from their enemies. These tubes can be found as isolated specimens or attached to larger shells. Two genera, Serpula and Hamulus, are fairly common in formations near the C&D canal.

Clams, Snails, and Squid: Phylum Mollusca, Class Cephalopoda

Cephalopoda is the scientific name for the mollusc group that includes the chambered Nautilus, squid, and octopus. Two extinct types are found at the C & D canal: the Nautilus-like ammonites and the superficially squid-like belemnites. Ammonites are uncommon, especially complete specimens, but can be very useful for age determination. The belemnite species Belemnitella americana has been so abundant at some canal localities that it was named the state fossil of Delaware.

Magothy Formation

Dark-gray to gray silty clay to clayey silt that contains abundant fragments of lignite; grades downward into a very fine to fine sand with scattered and discontinuous thin beds of clayey silt with lignite fragments. Thickness ranges from 20 to 50 ft. Updip in the vicinity of the Chesapeake and Delaware Canal, the Magothy fills channels incised into the Potomac Formation and is discontinuous in its extent. Interpreted to have been deposited in coastal to nearshore environments.

Merchantville Formation

Light- to dark-gray, very micaceous, glauconitic, very silty fine- to very fine-grained sand to fine sandy silt. Ranges from 20 to 120 ft in thickness. Marine in origin.