There are two very nice sized Orthoceras in Matrix Specimens. 
A: The larger of the two measures approx. 7" x 5": thickness 1.6": weight is 1.036 kGrams.
B: The smaller of the two specimens meaures approx. 110 x 99 mm: thickness is 42 mm: weight is 461 grams. 
 
Orthoceras 
are extinct cephalopods with a horn or straight shell. Orthoceras grew its own shell. It could grow up to 14 feet. It was a hunter that had a flexible diet. The fossils of these creatures are found worldwide. They were the ancestor of the nautilus family and some of their family members still exist today