182 J. F. KEMP — THE LEUCITE HILLS OF WYOMING. 



The rocks of the Leucite hills, it seems to the writer, are best described 

 as leucite-phonolites which shade into leucitites or related rocks, by 

 which name they have been usually called, as the result of Zirkel's earlier 

 observations, and before the presence of sanidine was known. Zirkel 

 himself merely places them with the leucitites in his recently published 

 and invaluable Lehrbuch der Petrographie. The forthcoming paper of 

 Dr Cross, elsewhere referred to, will doubtless settle their systematic 

 relations by means of additional analyses. 



