324 



ALLIS: [Vol. XVIII. 



EXPLANATION OF PLATE X. 



Fig. 56. Ventral view of the anterior end of the head; with the outer 

 skin removed, and the mandibles spread apart so as better to show the 

 muscles. X 2. 



Fig. 57. The same, a slightly deeper dissection. X 2. 



Fig. 58. The same, a still deeper dissection. X 2. 



Fig. 59. Dorsal view of the branchial arches, with the associated muscles, 

 nerves and arteries. The skull and spinal column have been removed by 

 cutting the nerves and muscles, and the muscles that were attached to the 

 skull have been allowed to fall mesially and downward onto the arches 

 and considerably out of their natural position. The levator of the fifth 

 arch is shown as a small bit of muscle attached to the nerve that inner- 

 vates it. X 3. 



