The reptillian brain is made of the brain stem and the cerebellum. The cerebellum is like an apple hanging off the back, and the brain stem is the medulla oblongata, which looks like it's the spinal cord trailing off down the bottom, the pons, which connects the MO and the cerebellum, and the midbrain, which sits on top of the pons.

A frog's brain is like just the reptilian part of our brain.