Extended HD partition is listed in fstab and has an /mnt entry, see /mnt/hda4 below:
# /etc/fstab
proc /proc proc defaults 0 0
sysfs /sys sysfs defaults 0 0
devpts /dev/pts devpts defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
/dev/hda /mnt/hda auto noauto,users,exec 0 0 # Added by TC
/dev/hda1 /mnt/hda1 ext3 noauto,users,exec,relatime 0 0 # Added by TC
/dev/hda2 /mnt/hda2 ext3 noauto,users,exec,relatime 0 0 # Added by TC
/dev/hda3 none swap defaults 0 0 # Added by TC
/dev/hda4 /mnt/hda4 auto noauto,users,exec 0 0 # Added by TC
/dev/hda5 /mnt/hda5 ext3 noauto,users,exec,relatime 0 0 # Added by TC
Doesn't harm, but definitely not needed and can be misleading.
/dev/hda like entry was already discussed in the summer; Curaga (if I remember well) had a comment on certain badly partitioned MP3 players which can't be mounted on a usual way as /dev/sda1 only as /dev/sda However it is rare exception, would be better to remove these entries too.