phone number missing from iMessage on iPad

I upgraded to an iPad Air a few months ago. Ever since, I haven't been able to get it to send or receive mesages from my iPhone's phone number. Previously with iOS 5 with my first-gen iPad this worked fine.

I've looked at the support article on this here: http://support.apple.com/kb/HT5538, but it doesn't seem to help. On my iPhone, I can send and receive from my phone number and my Apple ID email address. I can do the same from my MacBook Pro running 10.9. But I do not see any phone number listed as an option on my iPad, only my Apple ID is listed.

I've tried disabling and re-enabling iMessage on both devices with no change.