BULL. GEOL. SOC. AM. 





VOL. 25, 1913, PL. 18 





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Figure 1. — Pilloav Laaa at Point Bonita, Marin County^ California 



The masses of lava up to 3 feet, rarely 5 feet, in diameter. Photograph by Prof. A. C. 

 Lawson, loaned by Dr. F. L. Ransome 



Figure 2. — "Elliusoidal Structure in intrusive Basalt'^ (Lawson) 



The locality is Hunter Point, San Francisco Bay, California. I'hotograph from the U. S. Geo- 

 logical Survey. San Francisco Folio, plate v 



PILLOW LAVA AND "ELLIPSOIDAL STRUCTUEE IN INTRUSIVE BASALT" 



