68 



The lherzolite described in this paper affords a good 

 example of an unaltered peridotite, no serpentine being ob- 

 served microscopically, and a low percentage of ferric oxide 

 and no carbon dioxide by analysis. 



In conclusion, I wish to convey my thanks to Dr. D. 

 Mawson for advice and assistance in the preparation of this 

 paper. 



University of Adelaide. 



EXPLANATION OF PLATE XIX 



Fig. 1. Basal section of enstatite, showing outlines of 

 lamellae twinning and poeciliticaHy intergrown olivine. (xl5) 



Fig. 2. Vertical section op enstatite, showing partial de- 

 composition to bastite and poeciliticaHy intergrown diallage. (xl5) 



Fig. 3. Section, showing enstatite with bastite, olivine, dial- 

 lage, and chromite. (xl5) 



Fig. 4. Lamella twinning and parallel intergrowths of 

 diallage with enstatite. Crossed nicols. (x42) 



