CORRECTIONS. 



A change in the arrangement of the Plates, after a part of this Memoir was printed, makes a few 

 corrections of reference necessary. 



Wherever on pages 6, 7, and 8 Plate XI is referred to, it should read Plate XII. 



Page 1, line 19 from bottom, for Fig. 3, readYig. 2. 



Page 7, line 16 from bottom, for Plate IX, Fig. 2, read Tlate X, Fig. 1. 



