30 ^^y- [Vol. IV. 



sends upward and backward a strong process between the 

 squamosal and the otic capsule, and that the lower border of 

 this involves the greater portion of the columella. As far for- 

 ward as the quadrate the squamosal rests on the columella, the 

 process just mentioned springing from the inner border of the 

 columella. This relation is shown in Fig. 9. 



If we consider how firmly the quadrate is clamped to the 

 skull by means of the squamosal, how greatly movements of the 

 columella must be restricted by its close connection with the 

 squamosal, and how the backwardly directed process of the 

 quadrate adds to the stability of the parts, we can easily believe 

 that the delicate structures of the labyrinth will be but little 

 disturbed by movements, even the most violent, of the jaws. 

 Since the AvipJiinma, as has been shown both by the observa- 

 tions of Dr. Shufeldt {Science, Vol. II, 163) and myself, attacks 

 its enemies with great vigor, seizing them between its jaws and 

 turning about its long axis like a drill or whirling around in a 

 spiral, it would appear necessary to protect the delicate organ 

 of the ear from such agitation as might during such conflicts be 

 imparted to it through the columella. 



The facial nerve is plainly seen to escape beneath the col- 

 umella. This is shown in Fig. 10, VII. 



The principal part of the ossification of the quadrate is found 

 on the outer surface of the cartilage. It is overlapped by the 

 squamosal, and along its outer border sends out a ledge which 

 supports this bone. The remarkable process sent backward by 

 the quadrate has already been mentioned. It may be called the 

 columellar process of the quadrate. 



The pterygoid cartilage, which in the larva consisted of a 

 slender rod unconnected with the suspensorium, has now joined 

 the lower border of the ascending process about one-third of the 

 distance back of where the latter unites with the trabecular car- 

 tilage. The pterygoid bone is present as a very thin and 

 slender splint, which posteriorly forms a suture with the inner 

 side of the quadrate, and runs forward beneath first the ascend- 

 ing process of the suspensorium and then the proper pterygoid. 



Posteriorly the groove for the temporal muscle and tendon is 

 along the lower border of the parietal bone. When the prootic 

 bone is reached, the parietal overlaps it. Farther forward the 

 two bones form a harmonia suture. Near the anterior end of 



