22. 



lying just inside, and closely applied, to the wall, ia a ciiittaous 

 rod or plate, figure, 19, cr.. These rods are much heavier near 

 the median line^become thinner laterally, and finally disappear. 

 FurtZaermore the chittnoiis rod on each side of each plate is con- 

 tinuous with the chittnous rod of the opposing side of the plate 

 adjoining. Each rod, might then be described as hairpin shaped, 

 with two prongs, each of which extends along the innery,of the wall 

 of one side of one plate. Each plate receives one prong from 

 each of two hairpin shaped rods, figure 20 cr. 



Many of the muscle fibers of the suspensory membrane 

 are continued dOT/n along the inner surface of the anterior wall 

 of each plate, fig. 19 rap. These were supposed by Mitsukuri C^^) 

 to be chitenous rods but they were later sliown by Kellogg ('*)to be 

 muscles. They start from the suspensory membrane as bundles of 

 fibres, which branch and spread out as they descend. into a fan 

 •e h ft p e-. Manj'- of the fibers apparently find insertion in the wall 

 of the plate itself, but not a few are extended to the chitenous 

 rods and are inserted over thfir s^arfaces. Kellogg, no doubt 

 rightly, oonnootoi movements of the plates, which are common in the 

 gills of mutilated specimens, and in the excised gills themselves, 

 to these muscles. 



It can be seen in young specimens, where the gills can 



