THE CLUPEOID CRANIUM AND THE SWIMBLADDER 465 



sarily inconsistent with Herrick's account of these branches in 

 Menidia. 



The auditory nerve pierces the subcerebral plate of perilaby- 

 rinthine tissue (fig. 8, VIII) and divides into a saccular and a 

 utricular division. The saccular division passes backward under 

 the triangular plate of the exoccipital bone to the inner side of 

 the sacculus. Under the edge of this plate it gives off a branch 

 which passes over the sacculus to the posterior ampulla. The 

 utricular division divides into branches which supply the ampullar 

 organs of the anterior and horizontal semicircular canals and 

 the three divisions of the macula acustica utriculi. The two 

 branches to the ampullae are long; between them lie the two 

 short branches to the posterior and middle divisions of the 

 macula; the anterior division of the macula is supplied from the 

 anterior ampullar branch. 



The glossopharyngeal and vagus nerves leave the medulla 

 together. They emerge from the skull through the exoccipital 

 bone, though by different routes. The vagus passes through the 

 vagus canal; the glossopharyngeal nerve passes through its 

 foramen in the triangular plate of the exoccipital (fig. 4), traverses, 

 the upper part of the saccular portion of the auditory recess, 

 passes under the posterior ampulla, and penetrates the skull 

 just above the margin of the auditory foramen. The fusiform 

 bulla lies between the exits of these nerves. The glossopharyngeal 

 nerve gives a large communicating branch to the vagus as it 

 passes through the auditory recess and receives one from it 

 outside the skull. The vagal branch to the second branchial 

 arch has a separate ganglion. 



Just before entering its canal, the vagus gives off a branch, 

 the course of which is entirely intracranial. Its ganglion is at 

 its origin and gradually tapers off along its course. It passes 

 vertically upward in the perimeningeal tissue, at first just behind 

 the superior sinus of the labyrinth, but it gradually passes some- 

 what medial to it and in front of the supracerebral perilaby- 

 rinthine canal. In the perimeningeal tissue under the cranial 

 roof it divides into several branches. I have not traced all these 

 to their destinations; one contributes to the nerve supply of the 



