The growth of the calvaria is an integrated proce> s of osteogeriesis and of proliferation of tlicl intervening soft tissues within the originally membranous cranial capsule. At the onset of ossification each calvarial bone is surrounded hy a portion of this capsule which separates it from the adjacent bones. Any such soft tissue area map be regarded as a suture. However, at this early stage, this relatively undifferentiated tissue may properly be called a presumptive su-ture. The individual bones continue to increase in surface area during the period of growth until their definitive form is attained. As this occurs, the individual bones come into close approximation to each other. The plane of the suture perpendicular to the vault surface will describe the plane of articulation between these bones at the suture. In the period of definitive form it is proper to regard this relatively well differentiated tissue area as a definitive suture. Througliout this developmental process the sutural tissues proper, together with the peripheral edges of the adjacent bones, are regarded as the sutural areas.