Centroonoceras is a middle Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 cyrtoconic nautiloid cephalopod, otherwise similar to the orthoconic Sactorthoceras

Sactorthoceras

Sactorthceras is an orthoceratoid genus known from the Middle Ordovician of eastern North America , Norway and Korea and is the type genus of the Sactorthoceratidae....

and also included in the Sactorthoceratidae

Sactorthoceratidae

The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic siphuncle composed of slightly expanded segments and free of organic depsits...

. It was named by Kobayashi, 1934, and has been found in Korea and in New York state in the eastern U.S.

Centroonoceras is characterized by a smooth, gently expanding shell with a moderate but definite curvature and circular cross section. Septa are close spaced. The siphuncle is subcentral, as in Sactorthoceras. Segments are subfusiform; generally straighter on the dorsal side and more expanded on the ventral side. No cameral or endosiphuncle deposits are known.

References

• Walter C Sweet 1964. Nautiloidea-Orthocerida; Treatise on Invertebrate Paleontology, Part K. Geol. Soc. of America and Univ. Kansas Press.