ILLUSTRATIONS. 
Page. 
Plate I. Rhynchonellas of the Square Lake limestone 64 
II. Rhynchonellas of the Square Lake limestone 66 
III. ^4, Cleaved andesite, Edmunds Hill; B, Hobart Hill; massive andes- 
ite exposed by erosion 101 
IV. Map of Aroostook volcanic area 105 
V. A, Spherulitic rhyolite from Haystack Mountain; B, Vesicular lava 
from Haystack Mountain 107 
VI. A, "Birch bark" weathering of rhyolite; B, Transverse section of 
same 108 
VII. A , Andesitic lava; B, Andesitic breccia 112 
VIII. A, Fine-grained Sheridan sandstone; B, Sheridan sandstone 132 
IX. A, Conglomerate of the Sheridan sandstone series; B, Sandstone from 
Madawaska Lake 1 34 
X. A, Railroad cut at Houlton, showing slated Aroostook limestone; 
B, Railroad cut at Timony road, showing folded and faulted 
Aroostook limestone 140 
XI. A, Banded limestone; B, Aroostook limestone 142 
XII. A, Mapleton conglomerate; B, Manganiferous iron slate 144 
XIII. A, Perlitic type of rhyolite; B, Area between spherulites, perlitic 
type of rhyolite 1 58 
XIV. A, Vesicular lava; B, Volcanic tuff 160 
Fig. '.. Index map of area described 12 
2 View of Haystack Mountain 107 
3. Diagram of Haystack Mountain 109 
4. Section on Mapleton-Presque Isle road 1 13 
5. Hap of part of Mapleton Township, showing the teschenite area 116 
6. Map of Castle Hill area 1 20 
7. Se-tion at Mars Hill 135 
8. Section through Winslows Hill 137 
9. Microcline and orthoclase intergrowth 149 
10. Zoml intergrowth of microcline and orthoclase ...'.' 150 
1 1 . Optical measurements of a plagioclase crystal 182 
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