[Illustration: FIGS. 14-15. Transverse sections through skull: 14) at level of optic foramen; 15) at level of oculomotor foramen. Abbreviations: _angspl._ angulosplenial; _ant. r. pter._, anterior ramus of pterygoid; _ant. sq._, anterior arm of squamosal; _b. ang. o._, bursa angularis oris; _fpar._, frontoparietal; _fpar. fon._, frontoparietal fontanelle; _l. perp._, lamina perpendicularis of frontoparietale; _max._, maxillary; _Mc. c._, Meckel's cartilage; _ocul. f._, oculomotor foramen; _opt. f._, optic foramen; _pasph._, parasphenoid; _psdbas. proc._, pseudobasal process; _pter. proc._, pterygoid process; _scl._, sclera; _t. t. mar._, taenia tecti marginalis; _tymp. r._, tympanic ring.] _Pterygoid._--The anterior terminus of the pterygoid (_pter._, Fig. 1) appears at approximately the mid-length of the orbit as a small arcuate bone closely applied to the posterior maxillary process. Farther posteriorly the maxillary decreases in size, and the pterygoid and posterior maxillary process diverge medially from it. Posterior to this point of divergence, the posterior maxillary process is known as the pterygoid process (_pter. proc._). The anterior terminus of the quadratojugal (_qj._) lies medial to the maxillary at the level of the oculomotor foramen (Fig. 14). _Otic region._--The anterior end of the otic capsule (_ot. cap._) is present at the anterior level of the oculomotor foramen. The anterior terminus of the pseudobasal process (_psdbas. proc._) lies within the medial portion of the pterygoid at the posterior border of the oculomotor foramen (Fig. 15). The pseudobasal process abruptly increases in size. At the level of the prootic foramen (Fig. 16) the medial branch of the pterygoid diverges from the posterior ramus and is closely applied to the medial surface of the pseudobasal process. The otic process extends along the medial surface of the squamosal from the dorsolateral edge of the pseudobasal process, and then expands medially to meet the bony edge of the otic capsule and form the crista parotica. Posterior to the formation of the crista parotica, the ventral part of the otic process splits. The medial part forms the ventrolateral ledge of the otic capsule (_vl. l. ot. c._, Fig. 20a-f), whereas the lateral part moves ventrad in association with the ventral arm of the squamosal and fuses with the pterygoid process posteriorly. Posterior to the bony closure of the prootic foramen, the ventromedial part of the pseudobasal process joins the prootic and forms the ventrolateral edge of the otic capsule. The posterior terminus of the medial branch of the pterygoid lies ventral to the lateral part of the otic capsule. The posterior branch of the otic process merges with the pterygoid process ventrally.