Belemnites
Belemnitella americana (Morton)

 Belemnites belong to a diverse group of cephalopods which include the squid, cuttlefish and octopus, they are characterized by an internally chambered shell known as a guard. Looking like bullets or orange pens, Belemnitella americana is found in abundance at the Big Brook Fossil Preserve. The forward part of the guard (the back is the pointed end) has a V shaped chamber which was used for buoyancy control. Casts of these chambers called phragmocones are often mistaken for teeth. Belemnites can occur in huge numbers in some localities in so-called belemnite grave yards. 
 (Richards et al, 1962) only lists this single species as being present in New Jersey.

Belemnitella americana
These specimens have been polished up a bit.

Monmouth County, NJ

 

These belemnites were found split like this. This gives a good view of the chamber
used for buoyancy control.
 

Phragmocones
Internal casts of the chambers are common and easily mistaken for teeth by beginners.
Unlike shark teeth the casts are "cone like" with two ridges running down the sides.

A group of larger beleminites, the top one measures 4 1/4 inches.
In New Jersey the belemnite guard is usually amber colored, due to absorption of iron.
 
 

References

Richards, H., R. Ramsdell, A. Miller, H. Garner, J. Reeside Jr., A. Jeletzky, H. Roberts, and H. Miller Jr. 1962. The Cretaceous Fossils of New Jersey, Part
II. Bulletin 61, Bureau of Geology and Topography, Department of Conservation and Economic
Development, Trenton, NJ, 237 pp.