A comparative analysis is performed between high-quality integrated spectral indices of 30 globular clusters in M31 , 20 Milky Way globular clusters , and a sample of field and cluster elliptical galaxies .
We find that the Lick CN indices in the M31 and Galactic clusters are enhanced relative to the bulges of the Milky Way , M31 , and elliptical spheroids , in agreement with Burstein et al .
Although not particularly evident in the Lick CN indices , the near-UV cyanogen feature ( \lambda 3883 ) is strongly enhanced with respect to the Galactic globulars at metallicities , –1.5 < [ Fe/H ] < –0.3 .
Carbon shows signs of varying amongst these two groups .
For [ Fe/H ] > –0.8 , we observe no systematic differences in the H \delta , H \gamma , or H \beta indices between the M31 and Galactic globulars , in contrast to previous studies .
The elliptical galaxy sample lies offset from the loci of the globular clusters in the both the Cyanogen– [ MgFe ] , and Balmer-line– [ MgFe ] planes .
Six of the M31 clusters appear young , and are projected onto the M31 disk .
Population synthesis models suggest that these are metal-rich clusters with ages 100–800 Myr , metallicities –0.20 \leq [ Fe/H ] \leq 
0.35 , and masses 0.7 \sim 7.0 \times 10 ^ { 4 } \hbox { $ \thinspace M _ { \odot } $ } .
Two other young clusters are Hubble V in NGC 205 , observed as a template , and an older ( \sim 3 Gyr ) cluster some 7 kpc away from the plane of the disk .
The six clusters projected onto the disk show signs of rotation similar to the H I gas in M31 , and three clusters exhibit thin disk kinematics ( Morrison et al . ) .
Dynamical mass estimates and detailed structural parameters are required for these objects to determine whether they are massive open clusters or globular clusters .
If they are the latter , our findings suggest globular clusters may trace the build up of galaxy disks .
In either case , we conclude that these clusters are part of a young , metal-rich disk cluster system in M31 , possibly as young as 1 Gyr old .