This is a very unusual specimen of Isotelus gigas from the Ordovician of Ontario, Canada. This wonderful specimen was recently acquired from the famous Eugene Thomas Collection. The rare feature of this specimen is that it was found in the Bobcaygeon Formation, not the Cobourg or Verulam - Isotelus from the Bobcaygeon are extremely uncommon. This is a nice, large I. gigas - the LACK of genal spines is quite evident, and the small, crescent-shaped eyes are easily seen. The thick-shelled exoskeleton is well preserved, except for the restored tip of the tail. This is a very rare example of Isotelus gigas from the Bobcaygeon, direct from the Eugene Thomas Collection.