THE SKULL THE CRANIUM 



211 



by far the larger, forming almost all of the bulla. It is regularly 

 oval ; pointed in front, and rounded behind. The ectotympanic (Fig. 

 144) is a bony ring surrounding the external auditory meatus and 

 applied to the outer side of the entotympanic. It is not a complete 

 ring ; a short segment is wanting at the upper posterior part. As the 

 ectotympanic is wider in front above, where it turns backward to join 



FIG. 143. 



OUTER VIEW. 



INNER VIEW. 



POSITION OF ENTOTYMPANIC. 



the skull, than it is where it coalesces with the entotympanic below 

 the auditory meatus, it appears to be united to the entotympanic at 

 an angle, with its plane directed upward and outward from the plane 

 of the entotympanic. It will be noticed, also, that the anterior outer 

 part of the flattened rim of the bulla, applied to the skull, the part 

 which is supplied by the ectotympanic, is higher than the rest and 



FIG. 144. 



ctotympnnic 



OUTER VIEW. 



INNER VIEW. 



POSITION OP ECTOTYMPANIC. 



faces more obliquely outward and forward. The bulla, as a whole, 

 presents an external and an internal surface and a superior border 

 which is introverted and so wide that it may be termed a superior 

 surface. 



The external surface. The external surface of the entotympanic 



