G. C. Broadhead — Cambrian and the Ozark Series. 57 



4. In crystalline-schists. — Chlorite sericite gneiss and glau- 

 cophane schist, Japan ;* on ilmenite from mica-schist, Island 

 Groix, France ;f in gabbro-diorite (alteration product of horn- 

 blende), Chichibu, Japan.;}: 



The writer is indebted to Messrs. Diller and Pirsson for two 

 occurrences of piedmontite in quartz-porphyry which have not 

 as yet been described. The first is in the porphyries and f el- 

 sites of the Boston basin. Although Mr. Diller does not men- 

 tion this mineral in his paper on these rocks, it occurs in at 

 least six sections which were kindly loaned the writer for ex- 

 amination. From Mr. Pirsson the writer has a section of a 

 porphyry almost identical with the common South Mountain 

 type, which comes from the " Archaean area of Georgia near 

 Tennessee." It has a finely developed micropoikilitic ground- 

 mass, considerable rather pale piedmontite (perhaps witha- 

 mite), and is especially interesting as showing the persistence 

 of the rhyolite to the southern end of the Appalachian region. 



Petrograpkical Laboratory, Johns Hopkins University, 

 'Baltimore, March 24, 1893. 



Aet. VIII. — The Cambrian and the Ozark Series ; by 

 G. C. Bboadhead. 



In the Missouri Geological Report, 1873-74, the writer 

 announced the finding of Lingulella Lamborni Mk. in the 

 lower Magnesian limestone beds of Madison County and from 

 that evidence the beds were referred to the age of the Potsdam. 

 I have also obtained from the same beds a Scolithus and 

 Oholella polita. 



In various papers published by C. D. Walcott notably in 

 this Journal for December, 1884, and in Bulletin 81 of the 

 TJ. S. Geol. Survey — Correlation papers — Cambrian he has 

 referred the Potsdam group to the age of the Upper Cambrian. 



In an article by the writer of this paper read before the 

 Am. Assoc. Adv. of Science, Cleveland meeting, 1888, and pub- 

 lished in the American Geologist, January, 1889, entitled 

 " The Geological History of the Ozark Uplift," the rocks of 

 the Ozarks were defined and I made the statement that the 

 Magnesian Series of the Ozarks were equivalent to the Upper 

 Cambrian of C. D. Walcott. In a subsequent article published 

 in the American Geologist for July, 1891, entitled the "Ozark 

 Series " I have briefly described the several members of the 



*B. Koto: Jour. Coll. Sci., Imp. Univ. Japan, vol. i. p. 303, 1887. 



f Lacroix: Bull. Soc. fr. de Min., vol. xi, p. 148, 1888. 



% T. Harada : Die Japanischen Inseln, Erste Lief. Berlin, 1890, p. 75. 



