The =lateral portions= (_b_) of the occipital arise from the caudal margin of the basilar portion in the transverse plane; a short distance laterad of the line of junction they turn dorsad at an angle of nearly ninety degrees. They form the lateral boundaries of the foramen magnum and pass dorsally into the squamous portion. The external surface of each presents an elongated elevated spirally curved surface, the =occipital condyle= (_c_), for articulation with the atlas. A small part of each condyle is formed from the basal portion. The two condyles are separated from one another ventrally by a narrow notch, and each extends (laterad) along the border of the foramen magnum to a point slightly dorsad of the transverse diameter of the latter. Laterad of each condyle the bone is elevated into a blunt triangular projection, the =jugular process= (_f_), which covers the caudal end of the tympanic bulla. Between the jugular process and the condyle is a deep depression. The internal surface (Fig. 18) is concave dorsoventrally, following the outline of the foramen magnum. It is convex from side to side. It is smooth except at its outer margin, which is rough for articulation with the mastoid portion of the temporal bone. The cranial face of the jugular process (_f_) shows a rough concavity for the reception of the bulla tympani. Mediad of the jugular process is a notch (=jugular notch=) (_g_) which when the bones are articulated forms part of the boundary of the jugular foramen. Mediad of this notch is a foramen which forms one end of the =hypoglossal canal=. It passes dorsocaudad into the cranial cavity and transmits the hypoglossal nerve. Dorsad of the hypoglossal canal is the cranial opening of the =condyloid canal=, which passes caudad and opens just craniad of the dorsal end of the condyle. It transmits a vein. The outer border of this portion is rough for articulation with the petrous and mastoid portions of the temporal. The =squamous portion= (_c_) has the form of a sector of a circle whose arc is a little more than ninety degrees. The central angle of the sector is truncated and bounds the foramen magnum dorsally. The arc of the sector forms the dorsal margin of the bone, while along the radii it passes into the lateral portions. Its dorsal portion is thick and porous; its ventral portion near the foramen magnum is thin and compact. The external surface (Fig. 17) is marked by a prominent ridge, the =lambdoidal ridge= (_h_), parallel with the dorsal border and near to it. The narrow portion of the outer surface that lies dorsad of the ridge forms an angle of about ninety degrees with the remainder of the surface. A median crest (_i_) extends ventrad from the middle of the lambdoidal ridge toward the foramen magnum; this is the =external occipital crest=. At its junction with the lambdoidal ridge it is elevated into a tubercle, the =external occipital protuberance= (_j_).