342 ROBERT J. TERRY 



tween the paranasal and parieto-tectal cartilage, spaces remain, 

 one of which is traversed by the lateral branch of the nasal 

 nerve; this is the beginning of the foramen epiphaniale. The 

 overlapping and fusion in the ventral region occui-s between the 

 inroUed anterior and ventral margins, where, in later stages, the 

 lamina supraconchaUs and nasoturbinal are found. The forma- 

 tion of these parts, however, was not observed. The dorsal 

 margin of the parieto-tectal cartilage lies next the olfactory- 

 bulb and is joined with the commissm'a spheno-ethmoidahs. 

 The triangular parieto-tectal cartilage has grown backward 

 along the septum nasi nearly its full length, thus forming the 

 roof of the nose. Its caudal and lateral obUque margin enters 

 into the formation of the crista semicircularis. In its anterior 

 part it reaches, in a ventral direction, as far as the naso-lacrimal 

 duct. The lamina transversalis anterior is unchondrified. The 

 paraseptal cartilages are represented by incompletely chondrified 

 tracts, independent of other skeletal parts. 



PART II. DISCUSSION 

 Occipital region 



Basal plate. As we have seen, the first evidence of a basal 

 plate was in the form of a pair of small cartilages on either side 

 of the notochord of the occipital region, united anteriorly by a 

 hypochordal commissure. Wincza has aheady observed this 

 early form of the base of the cranium and called the two com- 

 ponent laminae the parachordal plates. 



Regarding the chondrification of the basal plate in mammals, 

 several authors have shown that the initial stage is character- 

 ized by the presence of a pair of cartilaginous centers or tracts, 

 one on either side of the notochord in the occipital region. 

 Parker refers to the basal chondrification in the embrj^o pig, 

 first (75), as the 'investing mass,' later (77) as the parachordal 



