  This paper discusses Swift observations of the gamma-ray burst GRB 050315
(z=1.949) from 80 s to 10 days after the onset of the burst. The X-ray light
curve displayed a steep early decay (t^-5) for ~200 s and several breaks.
However, both the prompt hard X-ray/gamma-ray emission (observed by the BAT)
and the first ~ 300 s of X-ray emission (observed by the XRT) can be explained
by exponential decays, with similar decay constants. Extrapolating the BAT
light curve into the XRT band suggests the rapidly decaying, early X-ray
emission was simply a continuation of the fading prompt emission; this strong
similarity between the prompt gamma-ray and early X-ray emission may be related
to the simple temporal and spectral character of this X-ray rich GRB. The
prompt (BAT) spectrum was a steep down to 15 keV, and appeared to continue
through the XRT bandpass, implying a low peak energy, inconsistent with the
Amati relation. Following the initial steep decline the X-ray afterglow did not
fade for ~1.2*10^4 s, after which time it decayed with a temporal index of
alpha ~ 0.7, followed by a second break at ~2.5*10^5 s to a slope of alpha ~ 2.
The apparent `plateau' in the X-ray light curve, after the early rapid decay,
makes this one of the most extreme examples of the steep-flat-steep X-ray light
curves revealed by Swift. If the second afterglow break is identified with a
jet break then the jet opening angle was theta_0 ~ 5 deg, and implying E_gamma
> 10^50 erg.
