taking lvm backup

[Tapas Mishra]

I checked this link
http://tldp.org/HOWTO/LVM-HOWTO/snapshots_backup.html
created a snapshot volume

lvcreate -L592M -s -n backuplv /dev/nintendo/lvm1
 Logical volume "backuplv" created


lvscan
  ACTIVE            '/dev/nintendo/lvm1' [100.00 GiB] inherit
  ACTIVE   Original '/dev/nintendo/lvm2' [150.00 GiB] inherit
  ACTIVE            '/dev/nintendo/lvm3' [50.00 GiB] inherit
  ACTIVE            '/dev/nintendo/lvm4' [100.00 GiB] inherit
  ACTIVE   Snapshot '/dev/nintendo/backuplv' [592.00 MiB] inherit
root@:~# mount /dev/nintendo/backuplv /mnt/backup/ -o ro

but when I tried to mount the snapshot volume

# mkdir /mnt/backup
# mount /dev/nintendo/backuplv  /mnt/backup

I got error as follows

mount /dev/nintendo/backuplv /mnt/backup/ -o ro
mount: you must specify the filesystem type

the filesystem type on original lvm is ext4 and a swap partition.

So what filesystem do I specify to mount the snapshot volume.