1893-] 
175 
[Davis. 
increased. The occurrence of submerged tree stumps about the 
Cape and tlie islands accords with this explanation, but does 
not demand it. 
EXPLANATION OF PLATES. 
I. 
Hornbleiulic grcanitite. 
Succonuessett. 
2. 
Quartz porphyry. 
South Yarmouth. 
3. 
Succonnessett. 
4. 
Granitite. 
South Yarmoutli 
5. 
Quartzite. 
" 
6. 
Gneissoid granite. 
" " 
7. 
Fiue sandstone. 
.. 
8. 
Quartzite. 
.. 
9. 
" 
Highland Light. 
10. 
Red sandstone. 
i; 
n. 
Compact sandstone. 
North Truro. 
12. 
It <4 
" " 
13. 
Fine grained sandstone. 
" 
14. 
" 
" 
15. 
Qnartz porphyry. 
Succonnessett. 
16. 
Banded argillite. 
North Truro. 
All the above are from Cape Cod, Mass., and were collected by W. M. 
Davis. Scale I of natural size. 
Plate 2. 
1. 
Cambrian quartzite. 
N. Tisbury, Martha's Vineyard. 
2. 
Granitite (waterworn). 
Succonnessett. 
3. 
Granitoid rock. 
Matakeset Creek, Martha's Vineyard. 
4. 
Diorlte. 
Squibnocket. 
5. 
Quartzite. 
Chilmark, Martha's Vineyard. 
6. 
" 
Highland Light, Cape Cod. 
7. 
Finegrained trap? 
South Yarmouth. 
8. 
Fine grained rock. 
Highland Light. 
9. 
Augen-gneiss. 
Matakeset Creek, Martha's Vineyard. 
10. 
Quartzite. 
N. Tisbury, Martha's Vineyard. 
11. 
Red felsite. 
South Yarmouth. 
12. 
Quartzite. 
Highland Light. 
13. 
Trap. 
Cambridge. 
14. 
Quartz. 
Martha's Vineyard. 
15. 
Quartz porphyry. 
" 
16. 
" 
Matakeset Creek, Martha's Vineyard. 
All the above are from eastern and southeastern Massachusetts. 
Those numbered 1, 3-5, 9, 10, 13-16 were collected by J. B. Woodworth ; 
2, 6-8, 11, 12 by W. M. Davis. Scale \ of natural size. 
