The bones of the braincase are largely inaccessible but a small inner ear opening, the "recessus tympanicus dorsalis", is visible.
The pyramid and adjoining part of the recessus ellipticus are perforated by a number of holes (macula cribosa superior).
It is globular in form and lies in the recessus sphricus near the opening of the scala vestibuli of the cochlea.
On the underside of the braincase there is a well-developed depression, the "recessus basisphenoidalis".
On the upper wall or roof there is a transversely oval depression, the recessus ellipticus, separated from the recessus sphricus by the crista vestibuli already mentioned.