158 bulletin: .museum of comparative zoology. 



is, in all probability, as previously shown, another bed of tillite. At 

 Squantum Head a bed of tillite lies to the north of the sandstone. 

 Under the tillite at Atlantic there occur contorted slate and sandstone 

 layers with a predominance of slate. Just north of the tillite at Squan- 

 tum Head contorted slate with a few sandstone layers appear. Now 

 these beds are not duplicated at Squantum Head as they should be if 

 doubled by folding. The order is what it should be if the beds were 

 not doubled. It is true that such intercalated beds as these are very 

 variable, and a bed in one outcrop might not correspond to a similar 

 bed similarly placed in another outcrop, but the close correspondence 

 of these beds at Atlantic and Squantum Head is more likely to mean 

 a similar order of deposition, and the chances of coincidence are rather 

 small. 



Slate layers, or " nests " are found, and also a few small fragments of 

 slate. These layers or "nests" of slate may be found in the first few 

 feet of tillite on both the north and the south sides of the Head. This 

 deposition would be possible either in an advance, or retreat, or sta- 

 tionary condition of the ice, so it might mean either top or bottom, and 

 could not be limited to one or the other. If there is no duplication of 

 beds by folding the thickness of the tillite is 600 feet, otherwise 300 

 feet. 



There is some evidence of floating ice at Squantum Head, in 

 boulders found in the slate. Plate 7 shows such a boulder. This 

 one is of amygdaloidal melaphyre twenty-seven inches long and four- 

 teen inches wide, and was found at the western extremity of Squantum 

 Head near the contact of the tillite with the slate. 



Shearing has been very intense at Squantum Head, producing a 

 cleavage with sharp dip to the northeast. 



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



Locality 14- Brighton. In a vacant lot west of 55 North Beacon 

 Street, there is an outcrop which has been a puzzle to local geologists. 

 The strike at this locality is E 8° S, and the dip 28° N. The matrix, 

 which is less abundant than the included pebbles, varies from arena- 

 ceous to argillaceous. There is stratification, and some assorting. 

 The thickness exposed is about seventy-five feet. The pebbles are 

 mostly rounded with a few angular and subangular examples. No 

 striated pebbles have been found. Slate fragments abound. Mans- 

 field (1906, p. 75) writes as follows in regard to this outcrop: — "This 

 ledge has given rise to some controversy because of the appearance of 

 slate masses that resemble clastic material but are two feet or more 

 in length and nearly a foot in width. It has been maintained on the 



