Volcjvno Ushima, Llzu. 95 



already been stated (pp. 24-25 ; PI. YL EF). Dykes are also 

 seen, one at the foot of the western wall of the crater-harbour 

 Habu'^ (3e ; p. 22 ; PL YL DE), and four on the ring-wall of 

 the somma indicated by x on the geologic map (PL Y. Ic and 

 2d). These are olivineless basaltic bandaite witli characters 

 similar to those of the first type of the somma lava. They are 

 of two types : — 



10) Olivineless basaltic bandaite (/). (PL IV. Fig. 3.) 



The rock of dykes piercing the cliff opposite to Fudeshima is 

 megascopically compact, non-vesicular and is sonipatic with mega- 

 phenocrysts of plagioclase, from 5 mm. downwards in diameter. 



Microscopically, the phenocrysts of calcic hytownite Ab^^kn^^ 

 are mostly in euhedral to subbed ral stout prismatic to equant forms, 

 and usually exhibit very faintly marked zonal structure. The 

 groundmass consists of light greenish augite, plagioclase, less calcic 

 than the phenocrystic one, and magnetite, arranged in texture 

 near tlie ophitic fabric. The characteristic feature of the ground mass 

 is higli crystallinity and high granularity, it being almost holocrys- 

 talline and centimilhmeter-grained. 



11) Olivineless basaltic bandaite {ß)- (PL IV. Fig. 4.) 



The rocks of the other dykes, of which the southernmost one 

 on the western ring- wall of the somma is taken as representative, 

 are gray, compact witliout any vesicles. The plagioclase pheno- 

 crysts are very smah, rarely over 1 mm. across, and are not 

 conspicuous though they are fairly abundant. A few hypersthene 

 phenocrysts are also seen. 



1) j&i? 



