PRIMORDIAL CRANIUM OF THE CAT 337 



the cartilaginous lateral wall of this region is deficient; here the 

 great notch, the incisura posttransversalis is found (figs. 2, 3, 4, 

 13, 29). This space is entered from behind and ventrally by the 

 • cartilaginous anterior maxillary process. The post-transverse 

 notch is closed toward the nasal mucosa, by a layer of mesen- 

 chyma and by the incisive and maxillary bones which lie just 

 outside the plane of the cartilaginous nasal wall (figs. 29, 30), 



The dorsal region of the lateral wall of the cavum nasi corre- 

 sponds on the exterior to the paries nasi as described on p. 380 

 and may, like it, be considered as presenting three divisions, 

 anterior, middle and posterior. 



In the anterior division (pars maxillo-nasoturbinalis) will be 

 included, for convenionc, the inner surface of the lamina supra- 

 conchalis, although, as will be seen later, its primary relation to the 

 components of the nasal side wall was not established. This 

 division, then, extends from the level of the fenestra narina to 

 the crista semicirculars, and is limited ventrally by the maxillo- 

 and atrioturbinals. The most cephalic portion reaches the 

 atrioturbinal ventrally, and forms the lateral boundary of that 

 part of the nasal cavity here designated the atrium. The atrio- 

 turbinal is in line with the maxilloturbinal but is separated from 

 that process by a notch, the incisura maxillo-atrioturbinalis. 

 The succeeding part of the anterior division stands opposite the 

 area of the lamina supraconchalis and sulcus lateralis of the ex- 

 ternal surface of the nasal capsule, and further includes the 

 maxillo-turbinal and crista semicircularis in its ventral and 

 caudal limits respectively. The maxilloturbinal, triangular in 

 general form, is continuous laterally by its base, with the paries 

 nasi at the eminentia lateralis. It stands mainly in a frontal 

 .plane; its medial margin, opposite the septum, inclines ventro- 

 caudad to meet the caudal margin at an angle opposite the 

 paraseptal cartilage. Anterior to the level of the paraseptal it 

 participates with the paries nasi in the caudal boundary of the 

 ■post-transverse notch; posteriorly to the paraseptal it forms, 

 by its free margin, a wide notch or sinus with the ventral free 

 border of the antoibital part of the paries nasi, both entering into 

 the boundary of the fenestra basalis. The maxilloturbinal 



