334 ROBEET J, TERRY 



of the vomer (figs. 2, 26, 27) embracing the ventral edge of the 

 septum nasi, hes at some distance behind the paraseptal. 



The fenestra narina (figs. 2, 3, 4, 13), oval with its long axis 

 dorso-ventral, faces rostro-laterad. Its medial boundary is 

 formed by the septum, the lateral and ventral by the lamina 

 transversalis anterior, the dorsal, by the paries nasi. The lat- 

 eral margin presents a deep notch, the incisura lacrimaUs, where 

 the naso4acrimal duct turns medialward toward its termination. 

 The ventral margin of this notch is formed by the sagittal por- 

 tion of the anterior transverse lamina; the dorsal margin by the 

 rostral extremity of the atrioturbinale, or inrolled ventral margin 

 of the paries nasi. The lacrimal notch is the meeting place of 

 two divisions of the fenestra narina, a dorsal and a ventral. 

 The former leads to the atrial region of the cavum nasi; the 

 latter division receives the naso-lacrimal duct and opens into 

 the inferor meatus. The names pars atrialis and pars lacri- 

 malis, respectively will be used in further reference to these divi- 

 sions of the fenestra narina. In the present stage the superior 

 alar process is represented in dense mesenchyma. It is chon- 

 drified in the 7 cm. embryo. 



Fenestra olfactoria (figs. 1, 13, 26). The paired, quadrilateral 

 olfactory fenestrae offer wide communications, in the present 

 stage, between the nasal and cranial cavities. Their position is 

 in the caudal half of the nasal capsules, that is, in the subcere- 

 bral division, between the tectum nasi, anteriorly, and the roof 

 (lamina infracribrosa) of the posterior cupola, posteriorly. The 

 plane of each opening looks dorso-caudad and also somewhat 

 mesad. The anterior boundary, formed by the caudal free mar- 

 gins of the tectum nasi and prominentia lateralis, is considerably 

 wider than the posterior limit, made by the infracribrous plate. 

 The medial side is formed by the dorsal concave margin of the 

 septum nasi. The obhque lateral boundaries of the olfactory 

 fenestrae are formed by the dorsal margins of the prominentiae 

 laterales and the antorbital plates. On the anterior and lateral 

 sides of the fenestra olfactoria of the model are three processes, 

 the caudal extremities of the crista semicircularis, ethmotur- 

 binal I and ethmoturbinal II. Between these processes, the 



