Two Version of Rails on one machine


I installed rails3 on my mac and after installing 2.3.5 using gem
install rails -v 2.3.5, if I run gem list rails, I got
*** LOCAL GEMS ***

rails (3.0.0.beta, 2.3.5)

But if I run
rails 3.0.0.beta test
got the following error
can’t find executable rails for rails-3.0.0.beta (Gem::Exception)
from /usr/local/bin/rails:19:in `’

How can I create rails3 project?