472 



ANATOMY OF VERTEBRATES. 



320 



marked by a ridge continued from the lower border of the orbit. 

 The petrotympanic forms, in the smaller Musk-deer ( Tragulus) 

 and Antelopes ( Ceplialoplius), a large ' bulla ossea : ' and the orbits 

 gain in proportional size as the bulk of the species decreases. 

 The lateral emarginations of the bony palate are usually deeper 

 than the median one, in true Ruminants, the reverse being the 

 case in the Llama and Vicugna. In Micr other ium the premaxil- 

 laries do not reach the nasals, nor yet quite in Hycumosclius. 



In the skull of the Bovidce 

 I have usually seen that, al- 

 though the full size and mature 

 dentition have been acquired, the 

 suture between the exoccipitals, 

 fig. 320, n', u', and that between 

 these and the superoccipital, ib. 

 11, remain distinct. The occipi- 

 tal condyles, i, are wide apart, as 

 in Antelopes and Deer. The 

 paroccipital, i, and fig. 321, a'', 

 descends much below the mastoid, lo ; the exoccipitals complete the 

 foramen magnum, above : the basioccipital has a pair of tubercles. 

 In the Ox (^Bos faurus)the whole of the upper surface of the cranium 



321 



Skull of the Giiur, from behind. 



Skull of the Ox (Bos taurus). 



is formed by the frontals, fig. 321, c: the parietals, which, at 

 an earher period, encroach upon the back part of the upper sur- 

 face, are now pushed quite to the posterior or occipital aspect. 

 This deposition does not take place in the Bison, fig. 320, but the 

 frontals, at the interspace between the horns, are, with the con- 

 joined parietals, 9, developed into a ridge rising above that formed 

 by the superoccipital, ii. The petro-tympanic, fig, 320, lo, 321, e' , 

 is prominent and rough. The squamosal, e, has a venous outlet 

 above the base of the zygoma. The malar forms the lower part 



