The first Ceraurus I've ever found was from the Verulam formation and is pictured below. It's not complete but it is enrolled. You can see the stubs of one of the spines which extend from the Pygidium curving out.
Here is an angled view that shows the meet point between the Cephalon and Thorax
Based on the images in William Hessin's book "South Central Ontario Fossils", 2009, I am going to go out on a limb and say that this trilobite might be a Ceraurus globulobatus. I can'tr really be sure until I get the cephalon cleaned off a little more.
The specimen was collected from a quarry near Brechin, Ontario, Canada in the Verulam formation which is middle Ordovician in age (Katian/Mohawkian stage).