Irregular RPM indications on an SF340 lead to ultimate engine failure upon landing.

Narrative

While enroute from ZZZ1 to ZZZ; I noticed the left propeller RPM gauge showing between 1;000 RPM to 1;320 RPM. All other gauges appeared normal. I also noted engine vibration was unchanged; and yaw remained steady. After reaching cruise altitude; the left propeller RPM appeared to show a normal and stable RPM. Again on descent; the left PROP RPM began to show anomalous indications and the same range noted earlier. We began the landing sequence which requires the condition levers to be placed in the 'maximum' position. It was showing anomalous readings; but did change with the change in lever position. The needle on the gauge went past the green arc. Once again; all other indications appeared normal. Engine vibrations and yaw felt normal to those configuration inputs. Upon landing (flight idle stop light illuminated); with the power lever going from flight idle to ground idle; I felt and heard a power surge from the left engine. This was followed by loss of thrust; then the engine oil pressure triple chime. We exited the runway and proceeded with the emergency non-normal checklist and taxied to the gate.