494 



MISS JOAN B. PROCTER ON THE 



around the areolar is about twice as broad in front as behind, and 

 situated high up in the shield, the distance between it and the 

 vertebrals being less than the distance between it and the costal 

 posterior to it, and a quarter or less the distance between it and 

 the marginals ; in fact, the relative widths of the shield-borders 



Text-figure 6. 



Epidermal sliields of the plastron. (Adult ; J iiat. size.) 



(top : back : bottom : front) are roughly expressed by the geo- 

 metrical progression — 2 : 4 : 8 : 16. In jT. loveridgii this ratio is 

 better expressed — 4 : 2 : 4 : 5 or 4:1:4:6, the areolar being 

 midway between vertebrals and marginals, but situated very far 

 back in the shield. The areolar of the fourth costal is often 



