called " Steypirey^r " hy the Icelanders, 329 



If we first examine the atlas, it will appear, from the figure 

 given below (fig. 1) , that this vertebra presents all the cha- 

 racteristics peculiar to it in the Physalus section*, which 

 Mr. Flower first pointed out. Thus the rather long trans- 

 verse processes evidently enough arise from the upper half 



Fig. 1. 



Atlas, seen from behind, one-tenth of the natural size. 



of the sides of the vertebra ; they are somewhat compressed 

 at their base from before backwards, somewhat tapering to- 

 wards the end, and point straight outwards, except near the 

 very end, which is bent a little forwards. Further, we find, 

 on the posterior surface of the body of the vertebra, not two 

 separate, but only one single, horseshoe-shaped articular sur- 

 face for articulation with the axis ; and, finally, the vertebra 

 wants that median backward-directed triangular process which 

 in the Sihhaldms section projects from the under surface of its 

 body, and articulates with a special surface on the second ver- 

 tebra. The most important dimensions of the vertebra are the 

 following : — 



Distance between the extremities of the transverse 



processesf 30" 2'" 



Greatest height of the vertebra 15" 10"' 



Height of the neural canal 8" 4"' 



Greatest width between the outer edges of the arti- 

 cular cavities for the occipital condyles 15" 6"' 



Greatest diameter of each of these articular cavities 11" 9"' 

 Greatest breadth of the horseshoe-shaped articular 



surface for the axis 18" 2'" 



* Or to the genus Physalus^ Gray, of 1864, not 1866. 



t This measurement is not quite accurate, as the ends of both trans- 

 verse processes are a little damaged ; but the pieces broken off have pro- 

 bably not amounted to more than an inch on either side. 



