EAKLE. — ROCKS FllOM THE FIJI ISLANDS. 695 



show a different period of crystallization from tlie groundmass, and reach 

 a size to be designated as phenocrysts. 



The groundmass is pilotaxitic, consisting of short green augite micro- 

 lites, feldspar rods, and magnetite grains. No glass is present in the 

 base. 



The feldspar plates show an extinction angle of about \2° normal to 

 010, which indicates a soda-lime feldspar of an oligoclase or andesine 

 composition. 



The larger phenocrysts are olivine. They occur as rounded sections, 

 usually much corroded by ttie magma, and show alteration to serpentine 

 along the fractures. Ci'ystal sections and anhedrons of magnetite are 

 common. 



The above descriptions are made in the form of a report on the indi- 

 vidual specimens in the collection, and no generalizations are attempted, 

 because of the lack of sufficient representative material. Notes re- 

 garding the appearance and general structure of these volcanic islands 

 are not at hand, consetjuently the contents of this paper are purely 

 petrographicaL 



