342 Henry L. Brunei- 



epithelium of the lateral surface of the plica obliqua and farther 

 ventralward upon the caudal wall of the vestibule of the cavum 

 superius. This muscle may be assumed for the present to be a 

 derivative of the constrictor naris of the salamander. 



In addition to the two muscles above described, small isolated 

 bundles of smooth muscle fibers occur elsewhere about the caudal 

 wall of the vestibule of the cavum superius from which they radiate 

 in a caudal direction. Some of these bundles are shown in Fig. 1 1 , />, 

 PI. XVIII. 



c. The intermaxillary Mechanism immediately concerned 

 in Closing" and Opening the external Nares. 



The immediate cause of the closing of the external naris in 

 Eana is the movement of a horizontally placed, spoon-shaped car- 

 tilage (cartilago alaris), whose concave caudal portion closely invests 

 the nasal opening in front and laterally. This cartilage, which is 

 free from the skeleton both rostrally and caudally, rests with its 

 middle portion upon the anterior wall of the cartilaginous nasal 

 capsule, with which it is continuous by a narrow cartilaginous bridge; 

 beyond this bridge the cartilago alaris projects forward as a short 

 rod (processus praenasalis superior), which is attached to the dorsal 

 end of the hollow facial process of the intermaxillare {Pr.p.s., Fig, 9, 

 PI. XVII). The cartilago alaris thus forms a lever whose fulcrum 

 is at the point of union of the cartilage with the anterior nasal wall. 

 Below each processus praenasalis superior, we find a curved, rod- 

 shaped cartilage (processus praenasalis inferior), which arises from 

 the ventral surface of the cartilaginous nasal capsule and extends 

 forward until it meets the facial process of the intermaxillare medial 

 and ventral from the processus praenasalis superior (see Fig. 10, 

 PI. XVIII). Within the intermaxillare the processus praenasalis in- 

 ferior bends downward and enters the dentary process of that bone. 

 Each intermaxillare includes also a horizontal palatine portion which 

 is attached to its fellow in the median line and to the palatine 

 process of each maxillare by a loose syndesmosis. This mode of 

 attachment permits a slight movement of elevation and depression 

 of the median portions of the two intermaxillaria. On account of 

 the relations previously described, however, an elevation of the inter- 

 maxillaria will produce first, a divergence of their vertical facial 

 processes, second, a lateral movement of the two processus prae- 



