150 bulletin: museum of comparative zoology. 



The included fragments at the bottom are composed of granite, mela- 

 phyre, felsite, quartzite, and very large masses of slate. The largest 

 of the last measures at least six feet long by four feet wide. These 

 slate fragments become scarcer upward, and almost disappear. As this 

 exposure has been found very recently, no striated pebbles have as 

 yet been discovered. The boulders, boulderets, and pebbles observed 

 are angular and subangular for the most part, with rounded water- 

 worn individuals here and there. Pink granite predominates over all 

 other varieties of rock. This is true both for the underlying Roxbury 

 conglomerate and the tillite. Melaphyre is well represented and in 

 large fragments, as at the Squantum exposures. An intercalated bed 

 of conglomerate about two feet thick in the tillite, about 150 feet 

 above the sandstone is the ecjuivalent of a similar but thicker bed at 

 Squantum Head. Such beds in tillite are very variable. Shearing 

 has given a well-developed cleavage with sharp dips in a northerly 

 direction. 



Criteria found: — A, B, C, D, F, H, J, K, L, M. 



Locality 11. Atlantic-Squantum Knoll. To the north of Atlantic 

 on the road to Squantum and about three fourths of a mile southeast 

 of the aviation field there is a little wooded knoll where tillite is ex- 

 posed. It is not possible to be sure of strike or dip. Some inter- 

 calated beds occur on the shore, but they appear to be in blocks which 

 have been moved by' Pleistocene ice-action. About 100 feet of the 

 tillite bed is exposed in separate outcrops. The matrix at this ex- 

 posure is very fine, suggesting the lower part of the tillite. The 

 included pebbles, boulderets, and boulders are of granite, melaphyre, 

 felsite, and quartzite. The shapes of the fragments are as usual, 

 angular and subangular, with a very few water-worn pebbles. As this 

 exposure has been discovered very recently no search for striated 

 pebbles or other marks of glaciation has been made. A block of 

 melaphyre was found in the southeastern extremity of the outcrop 

 showing a very angular outline. This block measures four feet long 

 and one foot wide. Cleavage is well marked. 



Criteria found: — A, B, C, D, J, K, L, M. 



Dr. F. H. Lahee, of the Massachusetts Institute of Technology, 

 has examined a specimen of tillite from this locality and writes me 

 (14 February, 1913) as follows: — • 



"The specimen of tillite, from which I had the two thin sections 

 made, was obtained on the eastern coast of a small hill at the head of 

 Quincy Bay, three quarters of a mile southeast of the aviation field 

 (Locality 11). 



