Explanation of Plates I — III. 



CORRECTION. 



Owing to an unfortvmate oversight, the numbers of these Plates 

 have been transposed. 



Plate I should be renumbered II. 

 „ II „ „ III. 



„ III „ „ I. 



On Plate I (as amended), Figs. 25 and 26 should be renumbered 

 15 and 20. 



