PKIMORDIAL CRANIUM OF THE CAT 341 



marily outgrowths of the septum is brought into question by the 

 fact that they are most deeply stained in the van Wijhe prepa- 

 rations in their lateral parts and less so next to the septum. 

 In the midline dorsally a deep groove, the beginning of the sulcus 

 supraseptalis, lies between them. Besides the paired parieto- 

 tectal cartilages, there is, in the nasal region of van Wijhe prepa- 

 rations of 15 mm., a mass of cartilage quite independent of 

 other chondrifying tracts. This is a curved plate, overlying, on 

 each side, the diverticulum of the cavum nasi, which later is 

 included in the recessus laterahs of the cartilaginous wall. This 

 cartilage may be referred to, tentatively, as the paranasal car- 

 tilage. The parietotectal and paranasal cartilages stand close 

 together, the one in front of the other. It is of importance to 

 note that the dorso-cephalic margin of the latter overlaps the 

 dorso-caudal edge of the former. Van Wijhe preparations of 

 17 mm. exhibit still a third chondrifying tract in relation to the 

 nasal wall (fig. 8). This is a small plate of cartilage at the 

 very back of the cavum nasi, on either side of the nasal septum. 

 It appears to be entirely free from the septum and paranasal 

 cartilage. This lamina antorbitalis, as it may be called, lies in 

 a plane anterior to that of the origin of the preoptic root from 

 the trabecular plate, and behind the paranasal cartilage. It is 

 curved about the caudal end of the nasal sac, thus indicating 

 the beginning of the posterior cupola. The anterior margin of 

 the antorbital lamina projects into the fold of ethmoturbinal I 

 behind the diverticulum of the lateral recess, and is overlapped 

 by the caudal edge of the paranasal cartilage. The latter is 

 larger than in the preceding stage and presents anterior and 

 ventral incurved margins, continuous with each other. The 

 ventral edge projects into the fold of the maxilloturbinal and 

 represents the base of the cartilaginous process of that name. 

 The anterior incurved margin overlaps the lateral and, at the 

 same time, caudal margin of the parieto-tectal, and fusion has 

 occurred to some extent between them. A double layered curved 

 ridge is thus formed, projecting into that fold of the nasal wall 

 which bounds the lateral recess anteriorly; this is the beginning 

 of the crista semicircularis. Where fusion has not occurred be- 



