The dorsal surface is triangular, with one apex of the triangle truncated, elevated, and directed craniad. This elevation is the =tuberculum sellæ= (_d_). Just caudad of the middle the surface presents a rectangular elevation with rounded angles, the =dorsum sellæ= (_e_). The cranial end of the dorsum sellæ presents at each dorsolateral angle a very small smooth tubercle which represents one of the posterior clinoid processes of man. Between this elevation and the elevated cranial end of this surface there is a deep excavation, the =sella turcica= (_f_), in which in the natural state is lodged the hypophysis. Near the cranial end of the sella is a small foramen, probably nutrient. At the caudal end of the body a slight notch (_g_) separates it from the wing: this notch forms a part of the =foramen lacerum=. Against this notch fits the apex of the petrous bone, and from it a groove (=carotid groove=) is continued mediocraniad to the sella turcica. The ventral surface (Fig. 41, 3) is triangular, smooth, and nearly flat; it is marked by a median ridge which is the continuation craniad of the ridge on the ventral face of the basilar portion of the occipital. Its caudal angles are separated from the rest of the bone by sharp triangular elevations, laterad of which are rough triangular areas, overlaid when the bones are articulated by a triangular spine from the tympanic bulla. Its lateral surfaces are mostly covered by the wings. They appear at the sides of the elevated cranial end of the dorsal surface as triangular areas. The caudal end is concave, rough, and has the form of the cranial end of the basilar part of the occipital. The cranial end is nearly square and rough for articulation with the body of the presphenoid. =The Wing= (=alisphenoid=; ala magna of the human sphenoid) (Fig. 20, _b_).--This is a thin quadrilateral plate of bone attached by its medial border to nearly the whole of the lateral surface of the body. Its middle portion lies nearly in the same plane as the body, but its ends are curved dorsad so that its internal surface is concave and its external surface is convex. The curvature is most pronounced near the long lateral border, so that this border forms nearly a semicircle.