Q:

Can't modify partitions

I was beta-testing an Operating System and set up a separate 50 GB partition on my single 500 GB SSD. Now I cannot remove the beta partition. It shows up as another disk entirely. What can I do?

As you can see, I can't make any modifications to the partition structure (no + or - available, nor can I rename a partition). I should also add that the primary 450 GB partition is encrypted with FileVault 2, but the beta partition was not encrypted.
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         447.6 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:          Apple_CoreStorage                         51.1 GB    disk0s4
   5:                 Apple_Boot Recovery HD             650.0 MB   disk0s5
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS β                     *50.5 GB    disk1
                                 Logical Volume on disk0s4
                                 27FE73A1-740C-4600-B2C1-7252F1279293
                                 Unencrypted
/dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macintosh HD           *447.3 GB   disk2
                                 Logical Volume on disk0s2
                                 4E37E178-D9FC-4D18-8157-E57A65AB283B
                                 Unlocked Encrypted

A:

Thanks @Tetsujin. The listing looked a little screwy so I was a little hesitant to go mucking around with the command-line diskutil. But I ended up doing a diskutil corestorage list and then 
diskutil corestorage delete [UUID of 50GB Logical Volume Group]
GUI Disk Utility correctly saw the 50 GB of empty space as part of the other Logical Volume Group and I was able to delete it and merge it back in fine.

