250 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
of one stratum occur as pebbles in another stratum in a number of 
widely separated localities. None of the pebbles, however, display 
markings other than the pressure striations and indentations men- 
tioned above. 
In color the sediments of the three basins would meet the expecta- 
tion suggested by the table. 
Frequent alternations of coarse and fine beds occur in all the basins, 
especially in the vicinity of the finer sediments. Current markings 
and oblique lamination do occur, but they are relatively infrequent. 
Well-marked local unconformities have been observed in the Narra- 
gansett Basin near Attleboro, and in the other basins evidences of such 
conditions are furnished by the pebbles of contemporaneous sandstone, 
grit, and conglomerate found in the conglomerates at several localities. 
The limestone found in the Norfolk and Narragansett Basins consist 
of amorphous carbonate of lime and is not of organic origin. 
Crush. The Carboniferous sediments of the three basins present 
little resemblance to crush-conglomerates, according to the charac- 
teristics of the latter outlined in the table. The subangular shapes of 
the pebbles and the occurrence of fracture planes and tension cracks 
in some of the pebbles are the only similarities observed. 
Glacial. Nothing definitely comparable to glacial boulder-clay. 
has been observed in the conglomerates of any of the basins. The 
grains of the matrix are both coarse and fine and generally angular 
or subangular. No cases have been observed where the same grain 
appears partly angular and partly rounded. Broken grains of feld- 
spar are often present in the matrix but they usually show some sign 
of alteration. Occasionally, however, they are relatively fresh. The 
matrix cannot be said to be as compact as in the specimen of the 
Dwyka Conglomerate studied by the writer. * 
The pebbles are generally of local material but it has been observed 
that in the case of two varieties the source may have been remote- 
Generally there is little assortment either of size or kind. At Squan- 
tum and at Huit’s Cove in Hingham boulders several feet in diameter 
occur among smaller fragments in heterogeneous arrangement, but 
these are exceptional and very local occurrences. The larger boulders 
at these localities do not appear to have come from a remote source? 
but are of rocks similar to those now occurring along the margin © 
the basin. The pebbles of the various conglomerates do not show 
the characteristic traits of glacial pebbles and do not bear any glacial 
markings. 
The colors of some parts of the conglomerate series would corre- 
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