CEPHALOPODS are a class of MOLLUSKS represented here by the NAUTILOID fossils pictured on the opposite page. These have external chambered shells containing dividing partitions. The last and largest chamber encloses the soft body and is known as the living chamber. In life, the living chamber was connected with the other chambers by means of a calcareous tube (siphuncle) back to the smallest and earliest-formed chamber (protoconch). These Paleozoic (Ordovician) Nautiloids had a straight conical shape and their two horny beak-like jaws were surrounded by dozens of tentacles. Nautiloids were probably the most formidable, predaceous carnivores of the time. They attained the largest size of any invertebrates, living or fossil, sometimes growing to over ten feet in length. The Pearly Nautilus is the sole surviving member of a great race that abounded in the Paleozoic seas.
The NAUTILOID to the left on the opposite page has a rounded cross-section on its straight conical shell. The one to the left is compressed and, while species with flattened shells did exist, it is most likely that the weight of superimposed layers of sediment accomplished this result over millions of years. The largest Nautiloid, which I collected from the limestone rocks at the riverbed near the banks below Baby Point, was 30 cm long and was also compressed. All samples were carefully loosened from limestone rocks using cold chisels and a hammer.
Other Cephalopods include squids, octopuses, cuttlefish, extinct ammonoids, and extinct belemnoids.