We resolve a significant fraction of globular clusters ( GCs ) in NGC 4921 , the brightest spiral galaxy in Coma . Also we find a number of extended bright star clusters ( star complexes ) in the spur region of the arms . The latter are much brighter and bluer than those in the normal star-forming region , being as massive as 3 \times 10 ^ { 5 } M _ { \odot } . The color distribution of the GCs in this galaxy is found to be bimodal . The turnover magnitudes of the luminosity functions ( LF ) of the blue ( metal-poor ) GCs ( 0.70 < ( V - I ) \leq 1.05 ) in the halo are estimated to be V ( { max } ) = 27.11 \pm 0.09 mag and I ( { max } ) = 26.21 \pm 0.11 mag . We obtain similar values for NGC 4923 , a companion S0 galaxy , and two Coma cD galaxies ( NGC 4874 and NGC 4889 ) . The mean value for the turnover magnitudes of these four galaxies is I ( max ) = 26.25 \pm 0.03 mag . Adopting M _ { I } ( { max } ) = -8.56 \pm 0.09 mag for the metal-poor GCs , we determine the mean distance to the four Coma galaxies , 91 \pm 4 Mpc . Combining this and the Coma radial velocity , we derive a value of the Hubble constant , H _ { 0 } = 77.9 \pm 3.6 km s ^ { -1 } Mpc ^ { -1 } . We estimate the GC specific frequency of NGC 4921 to be S _ { N } = 1.29 \pm 0.25 , close to the values for early-type galaxies . This indicates that NGC 4921 is in the transition phase to S0s .