  We present spectroscopic observations of galaxies in the fields of 10 distant
clusters for which we have previously presented deep imaging with WFPC2 on
board the HST. The clusters span the redshift range z=0.37-0.56 and are the
subject of a detailed ground- and space-based study to investigate the
evolution of galaxies as a function of environment and epoch. The data
presented here include positions, photometry, redshifts, spectral line
strengths and classifications for 657 galaxies in the fields of the 10
clusters. The catalog comprises 424 cluster members across the 10 clusters and
233 field galaxies, with detailed morphological information from our WFPC2
images for 204 of the cluster galaxies and 71 in the field. We illustrate some
basic properties of the catalog, including correlations between the
morphological and spectral properties of our large sample of cluster galaxies.
A direct comparison of the spectral properties of the high redshift cluster and
field populations suggest that the phenomenon of strong Balmer lines in
otherwise passive galaxies (commonly called E+A, but renamed here as the k+a
class) shows an order-of-magnitude increase in the rich cluster environment,
compared to a more modest increase in the field population. This suggests that
the process or processes involved in producing k+a galaxies are either
substantially more effective in the cluster environment or that this
environment prolongs the visibility of this phase. A more detailed analysis and
modeling of these data will be presented in Poggianti et al. (1998).
