Floor of body of lateral ventricle is formed by
Floor of body of lateral ventricle is formed by 

Caudate nucleus
Thalamostriate vein
Thalamus upper  surface 
Body of fornix upper surface

Rostrum of corpus callosum forms floor, septum pellucidum forms medial wall, and genu of corpus callosum forms anterior wall of anterior horn of lateral ventricle.
Septum pellucidum
Rostrum of corpus callosum
Thalamostriate  vein
Genu of corpus callosum