Green, Chorda 'Tympani i7i Selachians. 41"; 



tomosing with each other. The details of this anastomosis are 

 not exactly the same on the two sides of the specimen so far 

 as the smallest twigs are concerned, though the larger ones on 

 both sides are as figured. The chorda after the union of its 

 two chief roots runs down around the edge of the hyoid arch to 

 the ventral surface in the space between the latter arch and the 

 mandible, then running forward and inward along the inner 

 face of the mandible, keeping all of its course close under the 

 mucous lining of the mouth, until it reaches the ventral median 

 surface under the tip of the mandible. Its principal distribu- 

 tion seems to be to the strong crescentic fold of the mucosa 

 which projects up into the floor of the mouth just behind the 

 teeth of the lower jaw. Near the median line it anastomoses 

 with the terminal twigs of the r. mandibularis internus of the 

 facialis, as Stannius mentions. 



In the sand shark, Carchafts littofalis, we find the condi- 

 tions indicated on Fig. 2. The post-spiracular and pre-spirac- 

 ular nerves go out from the brain together for a short distance, 

 then the post-trematic, or hyomandibular trunk, turns caudad 

 and the palatine nerve cephalad. From the base of the palatine 

 four twigs are given off directed laterally. The first of these 

 is the true pre-trematic branch, which runs backward along the 

 caudal face of the upper jaw embedded in the mucous mem- 

 brane which forms the anterior (cephalic) wall of the spiracular 

 cleft. Here it divides, one twig passing directly to the pseudo- 

 branch, under which it breaks up, the other twig running a 

 little farther ventrally to supply the mucosa of the outer part 

 of the anterior wall of the spiracle adjacent to the pseudo- 

 branch. 



The second branch runs out laterally to the edge of the 

 roof of the mouth, where it turns down to supply the adjacent 

 mucosa. It is to be regarded as a detached filament of the r. 

 palatinus. 



The third and fourth branches run out laterally to the 

 inner surface of the palato-quadrate and then unite, afterwards 

 pursuing a course approximately parallel with that of the pre- 

 trematic ramus, but farther ventrally. Running back along the 



