Mine

artspace:~# cd;mkdir test123;sudo mount /dev/sda4 test123;dmesg|tail
mkdir: cannot create directory `test123': File exists
mount: you must specify the filesystem type
sda: assuming drive cache: write through
SCSI device sda: 246784 512-byte hdwr sectors (126 MB)
sda: Write Protect is off
sda: Mode Sense: 43 00 00 00
sda: assuming drive cache: write through
 sda: sda4
 sda4: <bsd: sda5 >
sd 1:0:0:0: Attached scsi disk sda
usb-storage: device scan complete
hfs: unable to find HFS+ superblock