THE BONES OF THE SKULL. 149 
7. THE INTERPARIETAL BONE. 
The interparietal (os interparietale) is a small, lozenge-shaped 
element, surrounded by the two parietal bones and the supra- 
occipital. It is the first of the membrane roofing elements of the 
cranium proceeding forward from the supraoccipital, and in the 
rabbit’s skull is not fused with the occipital segment. 
8. THE PARIETAL BONE. 
The parietal bone (os parietale) is a characteristic roofing bone 
covering a large portion of the middle cranial fossa. It is somewhat 
rectangular in shape, and is connected by serrate sutures with the 
surrounding elements and with its fellow of the opposite side, the 
sutures producing a characteristic pattern on the external surface 
of the skull. The sutures are medial, anterior, lateral, and posterior 
in position, and are designated respectively as saggital, coronal, 
squamosal, and lambdoidal. The posterolateral angle of the 
bone is produced ventrally into a long, curved Squamous process 
(processus squamosus), which lies in the angle formed by the ten- 
torium cerebelli and the lateral wall of the middle cranial fossa. 
It is not exposed to the external surface of the skull. 
9. THE FRONTAL BONE. 
The frontal bone (os frontale) is a paired element, lying 
directly in front of the parietal, and forming with its fellow of the 
opposite side the anterior portion of the roof of the cranial cavity 
and also a considerable portion of its lateral, orbital wall. Unlike 
the condition in the human skull, the two bones are separate 
throughout life, so that there is a permanent frontal suture. 
Each consists of a frontal portion (pars frontalis), the external or 
dorsal surface of which continues that of the parietal, and of an 
orbital portion (pars orbitalis), enclosing the dorsal portion of 
the orbit. The two parts are connected at the supraorbital 
border, with which is also connected the base of the divided 
supraorbital process. The anterior end of the frontal portion 
is deeply notched where it comes in contact with the nasal and 
