204 



Charles Searing Mead. 



mals. Ventrally, on each side, the septum is produced outward 

 into a thick mass of cartilage, the processus lateralis anterior 

 (Fischer), which forms the median border of the fenestra. Antero- 

 dorsally it thins out and, curving around the nasal opening, becomes 

 continuous with the tectum. Posteriorly it goes over into the lamina 

 transversalis anterior, from which there projects backward a short 

 process, the processus paraseptalis (Pis. II and III, proc. parasep.). 

 The precartilaginous tissue above mentioned, which lies in the 

 fenestra basalis, is connected with the end of this process. Opposite 



zao" post.^ 



nas.sept. 



int.sept. 



Fig. 11. Diagram showing bow the nasal capsule of the reptiles has prob- 

 ably given rise to that of the mammals. Entire line, reptilian capsule ; dotted 

 line, mammalian capsule. 



nas.sept., nasal septum ; int,scpt., interorbital septum ; pr.max.post., proces- 

 sus maxillaris posterior. 



to the point where the processus lateralis anterior becomes separated 

 from the septum, the former is produced into a short ventrally- 

 directed process which abuts against the anterior end of the pre- 

 maxilla. The lamina transversalis anterior, the small band which 

 bounds the fenestra narina behind, forms the only ventral connection 

 between the paries nasi and the septum. Immediately in front of 

 the lateral end of this band is a slender process, the cartilago ac- 

 cessorius (Fischer). It arises from the ventral border of the paries 

 nasi, extends diagonally outward, downward and forward and ends 

 in a bulbous expansion lateral to the outer angle of the processus 



