270 



ON THE STEUCTUEE OF THE SKULL. 



frontals. The orbi to-sphenoid and alisphenoid vary in size. 

 The squamosal is large, and is firmly fixed to the side of the 

 skull, forming part of the wall of the cranial cavity. The 

 periotic, usually anchylosed into one bone with the bullate 

 tympanic, sometimes enters largely into the wall of the cranium, 

 sometimes is almost altogether excluded therefrom by the 

 parietal, alisphenoid, and other adjacent bones, which send 

 prolongations over it. 



The maxillary apparatus is greatly elongated, so as to form 



"mx- 



U7V- 



EO 



rtc 



Z*r 



SO 



TO 



Fig. 107.— Upper, under, and side views of the skull of a foetal Whalebone Whale {Ealceni 

 australis). The jugal bones are absent. In the under view the palatine bono is acci- 

 dentally marked Pt instead of PI. 



