FIGURE 2. First lower and upper third molars of Microtus pennsylvanicus (2.1, FHSM 17019 Lm1; 2.2, FHSM 17031 LM3) and Microtus (Pedomys) parmaleei (2.3, FHSM 17023 holotype Lm1; 2.4, FHSM 17026 paratype RM3). Note cement-filled prism fold (arrow) in 2.3; this valley is filled with cement to the base of the tooth.