We describe the morphological composition of a sample of 518 galaxies in the field of CL1358+62 at z=0.33 , drawn from a large HST mosaic covering 53 sq .
arcmin .
The sample is complete to I =22 , corresponding to M _ { V } =-18.5 in the rest frame .
The galaxy morphologies have been independently classified by the authors of this paper and by Alan Dressler .
Dressler ’ s classifications place our work in context with the previous MORPHS study , and allow us to estimate the scatter between different sets of visual classifications .

We restrict most of our analysis to the brighter part of the sample , I < 21 ( M _ { V } < -19.5 ) , where the scatter between the two sets of classifications is \sim 1 in morphological type .
The scatter doubles at I = 22 , presumably due to the lower signal-to-noise and poorer sampling of faint , small galaxy images .
To I =21 the two sets of classifiers agree on the fraction of early type galaxies ( elliptical+S0 ) : 72 % .
We conclude that CL1358+62 does not contain the large population of spiral galaxies found in other studies of clusters at z \sim 0.3 , and that there is probably a significant spread in the degree of cluster evolution at intermediate redshift .

The two groups of classifiers differ on the relative fraction of S0 and elliptical galaxies .
We show that the distributions of ellipticities and bulge/total light can not resolve this discrepancy .
Nonetheless , we can derive significant constraints on physical models for the evolution of the galaxy population in CL1358+62 .
The higher ratio of S0 to elliptical galaxies ( 1.6 ) found by DF/MF/PvD requires that the evolution preserve the relative fraction of elliptical , S0 and spiral galaxies .
Alternately , the lower ratio ( 1.1 ) found by AD requires that the evolution preserve the early-type to spiral ratio while increasing the S0 to elliptical ratio .
In the latter case , a possible evolutionary mechanism is accretion of galaxies that predominantly evolve to S0 ’ s between z =0.33 and the present .

We use our large body of spectra to make the correspondence between spectral and morphological type .
Our data follow the pattern seen in the field at low redshift : emission line spectra are more prevalent among the later morphological types .
The 11 identified k+a galaxies ( absorption line spectra with strong Balmer lines ) have S0–Sb morphologies .