E. D. Cope, struck by the remarkable fact that the molar teeth, both upper and lower, of all the mammals from the Puerco or lowest Eocene horizon of North America carry three cusps arranged in ...

The aortic valve is normally tricuspid or trileaflet. When two of the cusps are fused together, the valve becomes functionally “bicuspid.” Most commonly, the right and left coronary cusps are ...