Glacial History of Netv England Islands. — Upham, 83 
bay, the same preglacial and warm temperate marine fauna 
flourished while the sea and land had nearly their present rela- 
tive levels, as is known by the abundant fragments of shells, 
representing more than fifty species but including none that 
has since become extinct, found in the till of the drumlins of 
Boston harbor and the mainland on the south. These Pleisto- 
cene fossils I think to have lived before the beginning of glacia- 
tion here, and therefore doubt the inference of Shaler that till 
was exposed under the Sankaty Head shell beds in the section 
reported by Desor and Cabot. More probably the continental 
elevation continued through the Glacial epoch or time of pre- 
dominant snow and ice accumulation. Its end by subsidence 
brought the Champlain epoch of glacial retreat, neither in- 
terrupted nor followed by any general ice advance. 
The Champlain depression of the land is thought by Shaler 
to have allowed the sea to cover the highest points of Cape Cod 
and Martha's Vineyard, the land being then at least 300 feet 
lower than now. But its reelevation is supposed by him to 
have been "exceedingly sudden," probably occupying no long- 
er time than a year. He remarks, in the report on Martha's 
Vineyard, that the absence of wave erosion and shore lines on 
the marginal moraines and the lower kames and plains indi- 
cates that they were not exposed to the action of the sea during 
even a month. Such rapid rate of epeirogenic uplift, alifecting a 
broad region, appears impossible according to any observed or 
conjectured relationship of the earth's crust and interior. When 
I attributed to the differential uplifting of the area of lake Agas- 
siz, between the times of formation of its upper and lower 
beaches, a maximum rate of about half a foot (or at times one 
foot or more) yearly, this seemed to me a very surprising and 
almost unparalleled epeirogenic movement. It is therefore my 
belief that no sudden and great uplift occurred, but that this 
region during the Champlain epoch had a somewhat higher 
level in relation to the sea than at present. The northern de- 
pression of the land lower than now I think to have reached no 
farther southeastward than to the vicinity of Boston. The 
great subsidence restoring a mild climate and causing the de- 
parture of the ice-sheet seems to have brought this region near- 
ly but not quite so low as it is to-day. 
Many wide river channek on Long Island, Martha's Vine- 
