/en·do·cra·ni·um/ (-kra´ne-um)
Noun
1. In comparative anatomy is a part of the skull base in vertebrates and represent the basal, inner part of the cranium. The term is also applied to the outer layer of the dura mater in human anatomy. (wikipedia.org)
2. The layer between the dura mater and the skull. (wiktionary.org)
3. Membrane lining the inside of the skull. (wordnetweb.princeton.edu)