English: Fig. 33.—Diagrammatic sections of various forms of teeth. I, Incisor or tusk of Elephant, with pulp cavity persistently open at base; II, Human incisor during development, with root imperfectly formed, and pulp cavity widely open at base; III, completely formed Human incisor, with pulp cavity opening by a contracted aperture at base of root; IV, Human molar with broad crown and two roots; V, molar of the Ox, with the enamel covering the crown deeply folded, and the depressions filled up with cement; the surface is worn by use, otherwise the enamel coating would be continuous at the top of the ridges. In all the figures the enamel is black, the pulp white; the dentine represented by horizontal lines, and the cement by dots. (After Flower and Lydekker.)