So to sum up all of what is shown in the enlarged photo of the depressed fracture, let me state the following
(and it is my opinion): The depressed fracture is almost a perfect oval, and in the only photo we have access to, it is covered in the posterior one-third with a layer of pericranial membrane which was left attached to the skull when the posterior scalp reflection was done by Dr. Meyer.
(One more thing here that I feel compelled to note... I have to say that after seeing the work done by other physicians on scalp reflection, the coroner in JonBenets autopsy is about the sloppiest butcher I can imagine. Ill add this to my list of failures on his part.)
The darkened areas in this part of the photo:
are hemorrhagic tissue -- not missing fragments of skull on the edge of the fracture as evidenced by the glistening light circled in the following photo (If the dark area is missing skull, there should be nothing there to reflect the light.):
There is one fragmented edge on the right anterior edge of the depressed fracture.
I believe this to be simply incidental and not related to the shape of the weapon that caused the fracture. It could have been a weaker spot in the skull, or it could have been a small spot in the surface of her skull that was slightly higher than the area around it causing it to see more impact from the weapon.
.