  The Type Ia SN 2000cx exhibited multiple peculiarities, including a lopsided
B-band light-curve peak that does not conform to current methods for using
shapes of light curves to standardize SN Ia luminosities. We use the
parameterized supernova synthetic-spectrum code SYNOW to study line
identifications in the photospheric-phase spectra of SN 2000cx. Previous work
established the presence of Ca II infrared-triplet features forming above
velocity about 20,000 km/s, much higher than the photospheric velocity of about
10,000 km/s. We find Ti II features forming at the same high velocity.
High-velocity line formation is partly responsible for the photometric
peculiarities of SN 2000cx: for example, B-band flux blocking by Ti II
absorption features that decreases with time causes the B light curve to rise
more rapidly and decline more slowly than it otherwise would.
  SN 2000cx contains an absorption feature near 4530 A that may be H-beta,
forming at the same high velocity. The lack of conspicuous H-alpha and P-alpha
signatures does not necessarily invalidate the H-beta identification if the
high-velocity line formation is confined to a clump that partly covers the
photosphere and the H-alpha and P-alpha source functions are elevated relative
to that of resonance scattering. The H-beta identification is tentative. If it
is correct, the high-velocity matter must have come from a nondegenerate
companion star.
