Plate X. 

 (Figures 64-72) 

 A series of sclieiuas stiowiug the number and relative position of the ele- 

 ments present in the fenestra vestibuli in the various groups of the tailed 

 Amphibia, together with the relation of these elements to the ear capsule, 

 suspeusorium, hyoid arch, M. opercularis, and facial nerve. It should be 

 stated that they are to show relations only ; the representation of the pro- 

 cesses of the palatoquadrate, for example, being purely diagrammatic. In 

 Fig. G7 the relation of the hyoid arch (H.) is intended to represent the con- 

 dition in certain forms only. 



