I have installed gnome-shell with

sudo apt-get install gnome-shell

and its successfully installed but I cant find it in the sessions list at login screen. what might be the reason ?

Here are the needed details

august@august-OEM:~$ ls  /usr/share/xsessions

awesome.desktop     cinnamon2d.desktop  xfce.desktop

cairo-dock.desktop  cinnamon.desktop    xubuntu.desktop



august@august-OEM:~$ apt-cache policy gnome-shell

gnome-shell:

  Installed: 3.8.4-0ubuntu5

  Candidate: 3.8.4-0ubuntu5

  Version table:

 *** 3.8.4-0ubuntu5 0

        500 http://in.archive.ubuntu.com/ubuntu/ saucy/universe i386 Packages

        100 /var/lib/dpkg/status

august@august-OEM:~$