246 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
eastern hemisphere at a time which may have been coincident with 
the deposition of at least a part of the Carboniferous series of eastern 
Massachusetts. The inauguration of these glacial conditions was 
doubtless gradual, and was probably due to causes sufficiently general 
to have affected regions remote from the area known to have been 
glaciated. 
The supposition of mountains to the east and southeast has already 
received some support from the discussion of the sources of material 
in the conglomerates. That mountain building occurred in New 
England in Precarboniferous times is indicated by the existing ranges 
along the western border of Connecticut and the states northward 
and by the metamorphic rocks of eastern New England that have 
trends similar to those ranges. Materials from these ancient moun- 
tains are included in the Carboniferous conglomerates, for Woodworth 
has observed cleaved pebbles of quartzite in the conglomerate near 
North Attleboro, in which the cleavage planes of any given pebble 
lie in positions entirely unrelated to those of neighboring pebbles or” 
to the present attitude of the inclosing rock (d, p. 181). The broad 
questions raised by the suggestion of the disappearance of a former’ 
mountain range or perhaps a more extensive land mass along what 
is now the coast of Massachusetts are beyond the scope of this paper; 
but it may be remarked in this connection that the abrupt breaks in 
the structure of the lands at the sea coast in many parts of the North 
Atlantic ocean are highly suggestive of down-faulting. The coasts 
of Nova Scotia, Labrador, Iceland, and southwest Ireland may be 
cited as cases in point. 
Summary of Geographical Conditions. (1) An attempt to restore 
the present beds to their previous undeformed condition shows that 
they would form a mass at least 60 miles long and 30 miles wide, 
attaining a height above their base of 12,000 feet toward the south 
but thinning down to 5,000 feet or less northward. 
(2) At the time of the deposition of the upper or Dighton Conglom- 
erate in the Narragansett Basin there was probably high land south 
and east of the Narragansett Basin and northwest of the Boston Basin, 
but prior to the deposition of the sediments the land now occupied 
by the several basins was without much diversity of form and of 
relatively low elevation. 
(3) The areas now occupied by sediments were not certainly out- 
lined as basins previous to the deposition of the strata. 
(4) The arkose and red beds indicate that the region was subjected 
to long subaërial decay under conditions of cool climate and moderate: 
or scanty rain fall. 
