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