Delaware designated belemnite as the official state fossil symbol in 1996 through the efforts of The Martin Luther King, Jr. Elementary School third grade Quest students of Kathy Tidball. Belemnite fossils can be found easily along the shores of the Chesapeake and Delaware Canal.

Marine molluscs related to modern day squid, octopus, and pearly nautilus, belemnites were present on the Earth for a period spanning over 140 million years and disappeared about the same time of the dinosaur mass extinction approximately 65 million years ago at the end of the Cretaceous Period.

Built for speed, belemnites are believed to have been efficient carnivores that caught small fish and other marine animals with ten hooked tentacles and which were consumed with their beak-like jaws.

Source:

Delaware Facts and Symbols: Official Delaware Website
Delaware State Fossil, The Belemnite: U of Delaware

Links:

State Fossils & Dinosaurs - 50 States