Spawning a p3at robot in gazebo

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Hi I am trying to spawn a p3at robot in gazebo. I am facing a error in the urdf file. Error looks like -

 Msg Waiting for master.[ INFO] [1442861989.783415793]: Finished loading Gazebo ROS API Plugin.
 Msg Waiting for master
 [ INFO] [1442861989.784748923]: waitForService: Service [/gazebo/set_physics_properties] has not been advertised, waiting...
 Msg Connected to gazebo master @ http://127.0.0.1:11345
 Msg Publicized address: 10.10.51.200
 [rospack] Error: package 'geometry' not found
 [librospack]: error while executing command
 [ INFO] [1442861990.183335154, 0.022000000]: waitForService: Service [/gazebo/set_physics_properties] is now available.
 [FATAL] [1442861990.183827994, 0.022000000]: Package[geometry] does not have a path
 [ INFO] [1442861990.256869294, 0.091000000]: Physics dynamic reconfigure ready.

 Msg Connected to gazebo master @ http://127.0.0.1:11345
 Msg Publicized address: 10.10.51.200
 [spawn_urdf-4] process has finished cleanly
 log file: /home/arpit/.ros/log/ee8fc064-6092-11e5-8b86-b8763fea9d09/spawn_urdf-4*.log
 [gazebo_gui-3] process has finished cleanly
 log file: /home/arpit/.ros/log/ee8fc064-6092-11e5-8b86-b8763fea9d09/gazebo_gui-3*.log

ERROR IS GEOMETRY PACKAGE NOT FOUND !! I have that package in my home directory as well as in the directory of the ros ( roscd geometry ).

MY error is at this place in urdf file -

    <geometry name="pioneer_geom">
          <mesh filename="package://geometry/meshes/p3at_meshes/chassis.stl"/>
     </geometry>

Please help !! Thanks :)

PS I am new to ROS.