The parieto-occipital fissure or sulcus, is an oblique sulcus which demarcates the occipital lobe from the parietal lobe on the medial surface of the cerebral hemisphere 1. The parieto-occipital sulcus joins the calcarine sulcus to form a pattern similar to the letter Y which has been placed sideways

frontal lobe, parietal lobe, occipital lobe, temporal lobe, sylvian or lateral fissure, central sulcus. They are made up of greyish-white matter

If you're referring to the cortex of bone, that would be trabeculae.

The answer is sulcus.

Promachoteuthis sulcus was created in 2007.