The bony dorsomedial part of the sphenethmoid diverges, forming the anterior border of the frontoparietal fontanelle (_fpar. fon._, Figs. 1 and 14). The entire fontanelle is covered with a layer of dense connective tissue continuous with that in which marginal bones and cartilage of the sphenethmoid lie, and which is discrete from the lower dermal layer of the overlying skin. At this level the braincase is U-shaped in cross-section. Ossification terminates first in the ventrolateral corners, followed by the lateral and dorsolateral areas. The bony support of the latter area is furnished by the lamina perpendicularis (_lam. perp._) of the frontoparietal (_fpar._, Fig. 14). Cartilage appears in the ventral part of the sphenethmoid in posteromost sections; at the posterior levels of the orbit the sphenethmoid is entirely cartilaginous. Orbital, Otic, and Occipital Regions _Orbital region._--The sclera (_scl._, Fig. 14) of the eye is cartilaginous. The optic foramen (_opt. f._) is large and lies in connective tissue at the posterior limits of the orbit and sphenethmoid. At the posterior levels of the foramen the dorsolateral cranial roof cartilages, taeniatecti marginales (_t. t. mar._) converge medially to form the posterior margin of the frontoparietal fontanelle and the tectum synoticum (_tect. syn._) of the occipital region. At the posterior levels of the orbit the bursa angularis oris (_b. ang. o._, Fig. 14) is present adjacent to the maxillary. _Nerve foramina of otic and occipital regions._--The trochlear foramen lies within the bony margins of the optic foramen. The trochlear nerve is located posterodorsal to the optic tract, and separated from the latter by connective tissue. The oculomotor foramen (_ocul. f._) lies in connective tissue posterior and ventral to the optic foramen (Fig. 15). Anteriorly, dorsally, and ventrally the foramen has a bony margin formed by the prootic (_pro._); posteriorly, only a thin layer of connective tissue separates the oculomotor from the large prootic foramen (_pro. f._). The latter is bordered by bone dorsally and by cartilage ventrally (Fig. 16). Posteriorly, bone separates the prootic foramen from the anterior acoustic foramen (_ant. acus._ _f._), through which the ramus acusticus anterior and medius pass (Fig. 17). An extremely narrow bridge of cartilage separates the anterior acoustic foramen from the larger posterior acoustic foramen (_post. acus. f._). The latter has a bony posterior margin and is widely separated from the bony jugular foramen (_jug. f._) posteriorly (Fig. 19).