1 88 THE SKULL. [chap. 



the cranium. These latter (Pa) form the greater part of the 

 sides of the narrow high temporal fossae, and are ankylosed 

 with the supraoccipital above, although the different elements 

 of the occipital are still distinct. The frontals (Fr) are broad 

 from side to side, being prolonged outwards into the arched 

 supraorbital plates, but are almost entirely covered by lamel- 

 liform extensions of the maxillae, which leave but a thin 

 strip of the frontals visible on the external surface of the 

 cranium. The temporal fossa is bounded below and in 

 front by a stout postorbital process of the frontal, very nearly 

 meeting the broad zygomatic process of the squamosal. The 

 orbit is elongated from before backwards ; at its anterior 

 extremity is a rounded antorbital prominence, formed by 

 the junction of the maxillae, frontal and malar; below, it is 

 bounded by a long and very slender styliform zygomatic 

 process of the malar, which arises from near the anterior and 

 inner angle of the body of the bone, and passes backwards, 

 slightly curved downwards, to articulate with the extremity 

 of the zygomatic process of the squamosal. There is no 

 distinct lachrymal bone, or canal. 



The special modification of the bones of the face has 

 relation chiefly to the peculiar position of the nasal passages, 

 which, instead of passing forwards above the roof of the 

 mouth to the anterior extremity of the face, are directed 

 upwards and somewhat backwards towards the vertex of the 

 cranium; the external narial orifices being situated quite on 

 the top of the head, the part which first appears above the 

 surface of the water when the animal rises for the purpose of 

 respiration. The whole nasal cavities are small, and they are 

 (as far as concerns their bony walls) simple canals, entirely 

 destitute of turbinals. Though their direction is in the main 

 vertical, they are not straight, but curve round the anterior 

 end of the brain cavity, both upper and lower orifices (an and 



