[ros-users] turtlesim package not found

Hi all,

I have just installed Ros ( sudo apt-get install ros-cturtle-ros)
I want to follow the tutorial (http://www.ros.org/wiki/ROS/Tutorials).
But I can't find the package turtlesim needed for the tutorial :

rospack find turtlesim
[rospack] warning: trailing slash found in ROS_PACKAGE_PATH
[rospack] couldn't find package [turtlesim]


Could anyone help me to install this package.

Thanks.