Encyclopaedia Britannica, 11th Edition, "Celtes, Konrad" to "Ceramics" / Volume 5, Slice 6

by Various

Fam. 2. Tropitidae. Shells globular, but having radiating and tuberculated costae. Thalassoceras, Permian. Tropites, Trias. Sibirites, Trias.

Fam. 3. Ceratitidae. Shells coiled, with a large umbilicus, terminal chamber short, sutures with simple saddles. Trachyceras, Upper Trias. Ceratites, Trias. Dinarites, Trias.

Some genera with helicoidal shells are related to these coiled forms, viz. Cochloceras, Trias; also some straight forms, e.g. Rhab-doccras, Trias.

Fam. 4. Pinacoceratidae. Shell compressed, smooth, terminal chamber short, sutures very complicated, convex. Pinacoceras, Trias.

Fam. 5. Phylloceratidae. Shell coiled, the whorls overlapping each other, sutures formed of numerous lobes and saddles. Phytloceras, Jurassic.

Fam. 6. Lytoceratidae. Shell discoid, whorls loosely united or uncoiled, sutures deeply indented, but with only three saddles and lobes. Lytoceras, Jurassic and Cretaceous. Macroscaphites, Cretaceous. Reunites, Cretaceous. Ptychoeeras, Cretaceous. Turrilites, Cretaceous. Baculites, Cretaceous.

Fam. 7. Ammonitidae. Shell coiled, with narrow whorls which do not embrace one another, aperture simple, a horny anaptychus present. Ammonites, Jurassic. Arietites, Jurassic. Aegoceras, Lias.

Fam. 8. Harpoceratidae. Shell discord and flattened, with a carinated border, aperture provided with lateral projections, a calcareous aptychus, formed of two pieces. Harpoceras, Jurassic. Oppelia, Jurassic. Lissoceras, Jurassic and Cretaceous.

Fam. 9. Amaltheidae. Shell flattened, with a prominent carina continued anteriorly into a rostrum. Amaltheus, Lias. Cardioceras, Jurassic. Schloenbachia, Cretaceous.

Fam. 10. Stephanoceratidae. Shell not carinated, but with radiating costae, which are often bifurcated, aperture often with lateral projections which contract it, aptychus formed of two pieces. Stephanoceras, Morphoceras, Pensphinctes, Peltoceras, Jurassic. Hoplites, Cretaceous. Acanthoceras, Cretaceous. Cosmoceras, Jurassic. Various more or less uncoiled forms are related to this family, viz. Scaphites, Crioceras, Cretaceous.