TABLE OF CONTENTS. 



Page 



Introduction 1 



Topography and General Outlines 8 



Eozoic Formations 13 



Naugus Head Series 14 



Huronian ............. 24 



Granite 27 



Petrosilex 45 



Relations of the Petrosilex to the Shawmut Group ... 47 



Details of the Petrosilex . 55 



Petrosilex in Newbury ........ 55 



Concretionary Structure ....... 57 



Petrosilex on Marblehead Neck and the Adjacent Islands . 63 



Petrosilex of the Lynn and Medford Area .... 74 



Petrosilex in Needham ....... 79 



Petrosilex in Dover, Medfield, and Dedham .... 80 



Petrosilex in West Roxbury, Hyde Park, Milton, and the 



Blue Hill Region 82 



Petrosilex in Hingham and Plymouth ..... 91 



Relations of the Petrosilex and Granite 95 



Diorite 101 



Hornblendic Gneiss, etc., — Stratified Group ..... 105 



Limestone ............ 112 



General Relations of the Huronian Rocks - 116 



Eozoic Formations, — continued . . . . . . . . . 123 



Montalban 123 



Gneiss 135 



Mica Slate 136 



Argillite 137 



Limestone ............ 139 



General Relations of the Montalban Rocks ..... 140 



Stratigraphy of the Nashua and Merrimac Valleys .... 154 



General Relations of the Older Crystalline Formations of Eastern Massa- 

 chusetts 161 



Shawmut Group 163 



Details of the Shawmut Group . 166 



iii 



