Can you only partition a hard drive once?
From what you have presented in your question, you are finished using the Disk Utility. When you install Ubuntu, you can use the tools provided by the Ubuntu installer to finish partitioning the drive. You can used these tools to do the following.

Delete the existing MS-DOS (FAT) formatted partition labeled UBUNTU.
Create a new partition for Ubuntu. You should give this the mount point /. If necessary, save some free space for the swap partition.
Create a new partition the desired size of the swap space. With the current releases of Ubuntu the creation of this partition is optional.


Note: Ubuntu will use the hidden EFI partition created when OS X was installed. This EFI does not appear in the image you posted. However, this EFI partition will appear in the Ubuntu installer when you change the partitioning. You can use the OS X command diskutil list to see all partitions including the hidden ones.