1 6 SCHALLER 



Three doubtful forms are also described. 



1 p 1 4.20.24.7 1, probably correct symbols, but considered 

 doubtful because the faces were too uneven to allow of satisfactory 

 measurement. 



2 q {2.16.18.1}, a doubtful form too rounded for definite deter- 

 mination. 



3 t 117.16.33.1}, a doubtful form too rounded and uneven to 

 allow of definite determination. 



Chemical Laboratory, United States Geological Survey. 



