ERRATA ET CORRIGENDA. 



Page 52, Hue 13 from bottom, and page 53, explanation of Fig. 3, d 



''(reversed)," 

 Page 8S, note §, for "Bristowe " read " Bristow." 

 Page 119, explanation of Fig. 1, line 3, after " stone " insert " /." 

 Page 120, line 7 from foot, after " except" add " Trophon clathratus and." 

 Page 123, line 2 from foot, /or *' of" read " as." 



