''Halloceras'' is a gyroconic rutoceratid from the Lower

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

of North America, with a subtriangular whorl section, narrow dorsum (on the inner side), divergent flanks, and broad, rounded venter (on the outer side), frills at various growth points, suture with shallow ventral and lateral lobes, and a small siphuncle near the venter. ''Halloceras'' was named by Hyatt in 1884. The type us ''Halloceras undulatum''.

References

*Bernhard Kümmel, 1964 Nautiloidea-Nautilida. Treatise on Invertebrate Paleontology, Part K, Mollusca 3. Teichert and Moore, eds. Geol Soc of America and Univ Kansas Press. Nautiloids Devonian animals Devonian animals of North America {{paleo-cephalopod-stub