ERRATA. 



On page 8, fifteenth line from top, for "are" read is. 



" 33, thirteenth line from top, for "is" read are. 



" 33> twentieth line from top, for "axis appears" read axes appear. 



" 33, twenty-first line from top, for "it" read the axial pla7ie . 



" 33) fourth and thirteenth lines from bottom, for "axis" read axes. 



" 195, twenty-first line from top, for "serpentized" read serpentinized. 



" 397> twenty-third line from top, for "applicable" read appreciable. 



" 404, eighth line from bottom, for"hypothesis" read hypotheses 



(vii) 



