Bellerophon, an extinct genus of molluscs, known as an abundant fossil. The shell is spirally coiled in one plane, and the outer margin has a deep notch. About 300 species are known, persisting from the Cambrian to the Carboniferous strata. Bellerophon has been bandied about from one division of molluscs to another. Montfort, who established the genus, placed it among cepha- lopods; till lately it was regarded as a heteropod; now it is placed among fissorbranch gasteropods, not far from the common car-shell, and nearer the family Pleurotomariidae.