EXPLANATION OF ILLUSTRATIONS 



All Figures are reproductions from Photograms, except Figures 

 15 and 16, which are from drawings by Mr. M. H. Lapidge. 



Figures 10, 11, 14, 17, 18, 19, 22, 32, 33, 34, 36, 41, 42, 43, 44, 

 48, and 50, are by Mr. Andrew Pringle, the remainder by Mr. E. C. 

 Bousfield. 



