Which mirror type is mounted below the flat mirror and provides a wide-angle, intentionally distorted view of the entire side of the bus up to the mirror mounts and the front of the rear tires?

AAMVA CDL Manual (nhcdm.pdf), Section 10.1.4 – Outside Left and Right Side Convex Mirrors, p. 10-2

Each exterior mirror type exists to cover a specific danger zone the driver cannot see directly. Knowing which mirror shows which zone is what lets a driver build a reliable, repeatable mirror-check sequence before moving the bus.