ERRATA. 



Page 21, Fig. 3, in place of x' read x, and in place of x read x'. 



Page 28, line 24, in place of 7A read 7B. 



Page 44, fifteenth line from bottom, in place of "shown in figure 16A and B", 



read "shown in figure 16E and F." 

 Page 46, line 5, in place of 18C read figure ISA. 

 Page 61, about middle of page, in place of 25A read 25B. 

 Plate 7, K and L, in place of anterior dorsals, read anterior caudals. 



