The optimum stage of neurocranium of Corvus has been studied. The lordosis of the basal plate is now less evident.
The basicranial fenestra has been formed by a resorption in the pre – existing cartilage of the basal plate. The notochord is embedded in the basal plate and exposed dorsally below the hypophyseal and basal fenestrae. The commissural exoccipitocapsularis connects the occipital arch and the prominentia ampullaris posterior. The commissura praevagalis connects the lateral edge of the basal plate with the auditory capsule. The fissure metotica is divided into apertura medialis recessus scalae tympani, foramen jugulare and fissura exoccipitocapsularis. The acoustic foramina are five in number. The cavum metoticum is opened anteriorly but closed posteriorly. The complete formation of tectum synoticum occurs by fusion of occipital arches ventrally in the mid – line. The remaining of extensive regression of the anterior orbital cartilage is the planum supraseptale. The fenestra septi interorbitalis is formed by the resorption of the pre – existing cartilage of the interorbital septum. The regression process affects the posterior orbital cartilages and the acrochordal cartilage. The crista parotica and the pila antotica spuria are well developed. The cartilage associated with the palatine is formed. The elements of the nasal capsules originate from three centers of chondrification; the intertrabecula, the planum antorbitale and the paranasal cartilage.