XVII 



CLASSIFICATION OF VOLCANIC ROCKS 



239 



SYNOPSIS 



I. Class. — Olivine Rocks (Plag., oliv.). 



1 Each division would theoretically also possess an orthophyric and a felsitic 

 order ; but these orders are not represented in my collection and need only be 

 mentioned. 



II. Class.— Augite Rocks (Plag., aug.). 



1 Not represented in the collection. 



