FIGURE 1. Morphology and outlines of the first lower molar. 1.1, photograph of the occlusal surface of Microtus arvalis. 1.2, outline of the same molar. 1.3, two hundred fifty outline coordinates running anticlockwise from the starting point marked by the arrow. AC, anterior cap. BRA, buccal reentrant angle. LRA, lingual reentrant angle. PL, posterior lobe. T, triangle.