Spurr — Scapolite Hocks from Alaska. 315 



sidered to belong to what might be called the scapolite-ada- 

 mellites, which would be a group under the monzonite family 

 where the scapolite partly takes the place of the feldspar. 



It would probably be best, however, to separate the scapo- 

 lite-feldspar rocks into a distinct class, and to give the groups 

 characteristic names, the analogy with the feldspar rocks being 

 expressed by writing in the tabulation each group laterally 

 opposite the corresponding group of feldspar rocks. Thus the 

 rock first described may be called yentnite, from the Yentna 

 River, instead of scapolite-belugite, but it may be written 

 opposite the belugite group ; the type would then be a biotite 

 yentnite. Similarly the quartz-scapolite porphyry from the 

 Kuskokwim* River might be called kuskite, instead of scapo- 

 lite-adamellite ; the kuskite group of the scapolite-feldspar 

 class of rocks could be written opposite the adamellite (or 

 quartz-monzonite) group of feldspar rocks, and the type might 

 be called a kuskite porphyry. 



* Eskimo Kuska, derivation uncertain, kivik, genitive kwim, river. 



Am. Jour. Sci. — Fourth Series, Vol. X, No. 58. — October, 1900. 

 21 



