Pay Rate and Negotiation with Recruiting Firms

I recently obtained a job through a recruiting agency. I wasn't aware of the pay rate until my manager showed me the pay rate at work.

The company I'm working for is paying the recruiting agency Robert Half $70 an hour and they are paying me $38 an hour.

I have a few questions:
• Is this normal or should I be making more?
• When negotiating a job with a recruiter / agency should I be asking what the pay rate is?
• And, is a recruiter required to show / tell me what the pay rate is?