braincase 
noun
The cranium.The bulk of the muscle mass was located in an adductor chamber between the braincase and the dermal skull bones....
- The fourth shot struck the skull above the occipital condyle and entered the braincase; it likely caused instantaneous loss of consciousness and death due to massive brain trauma.
- In contrast with the gorgonopsians, the jaw musculature in early therocephalians expanded dorsally over the braincase, leaving only a narrow sagittal crest between the adductor chambers.