FIGURE 2. A representative sample of individual and left-right variation in the shape of the first lower molar of four arvicoline species. Outlines of the left and right teeth of Arvicola terrestris (2.1), Microtus agrestis (2.2), M. arvalis (2.3), and M. oeconomus (2.4) are illustrated. The left tooth was flipped to facilitate comparison with the right.