List all devices connected, lsblk for Mac OS X
diskutil list will list all disks with their identifiers, even if unmounted.

/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Mac SSD                 150.0 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data Windows 8               100.1 GB   disk0s4
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *500.1 GB   disk1
   1:                  Apple_HFS George Garside          300.2 GB   disk1s1
   2:               Windows_NTFS GRGARSIDE               199.9 GB   disk1s2




For mounted disks only…

To find the raw device name (i.e. /dev/disk0s1) you can run df.

You can limit the results to locally-mounted filesystems, use df -Hl.
This results in a list of partitions and their raw device names, as shown below:

Filesystem     Size   Used  Avail Capacity  iused    ifree %iused  Mounted on
/dev/disk0s2   150G   130G    20G    87% 31761475  4859615   87%   /
/dev/disk0s4   100G    83G    17G    83%   184667 17015601    1%   /Volumes/Windows 8
/dev/disk1s1   300G   282G    19G    94% 68771109  4529660   94%   /Volumes/George Garside
/dev/disk1s2   200G   172G    27G    87%   144125 26731127    1%   /Volumes/GRGARSIDE