  We report low temperature magnetotransport measurements on a high mobility
(\mu=325,000 cm^2/V sec) 2D electron system on a H-terminated Si(111) surface.
While low magnetic field data indicate a six-fold valley degenerate system, we
observe the integral quantum Hall effect at all filling factors \nu<=6 and find
that \nu=2 develops in an unusually narrow temperature range. An extended,
exclusively even numerator, fractional quantum Hall hierarchy occurs
surrounding \nu=3/2, consistent with two-fold valley-degenerate composite
fermions (CFs). We determine activation energies and estimate the CF mass.
