DR. BUNDJIRO KOTO ON SOME JAPANESE ROCKS. 457 
portant group of andesites in which a rhombic pyroxene occurred as 
the predominating bisilicate. Mr. Whitman Cross and others had 
not relied on pleochroism as a means of distinguishing the rhombic 
pyroxene, but on the fact that the majority of the longitudinal 
sections, irrespective of pleochroism, gave straight extinction. The 
mineral in question had also been isolated and examined, both chemi- 
cally and optically, by MM. W. Cross, Iddings, Petersen, and himself, 
with results that clearly proved it to be a mineral of the hyper- 
sthene type. The existence of triclinic augite in association with 
this pyroxene had been practically given up by the author. 
Mr. Rurtzy also commented on the value of the paper, and the 
interest attaching to the hornblende crystals partly converted into 
augite. 
