Upham.l 
136 
[Dec. 19, 
Winthrop and Nahant. From this tract the southeasterly moving 
ice-slieet, plowing up the marine beds and their inclosed shells, 
with those then tenanting the sea, carried them forward to form a 
portion of the till of the drumlins. That the sea-bottom from which 
these shells were derived had been shallow is evident from the pre- 
dominance of the round clam, which, according to Professor Ver- 
rill, is seldom found in any abundance below five fathoms. 
Glacially transported shells and fragments of shells have been 
previously observed in till in Brooklyn, N. Y., where E. Desor and 
W. C. Red field gathered fragments of the round and long clams, 
oyster, and other species, “ imbedded in a reddish loam intermixed 
with pebbles and boulders, many of which are distinctly scratched j ” 1 
and in till, or at least deposits of clay enclosing numerous stones 
and boulders, on the lower part of the Saint Lawrence river, from 
the vicinity of Quebec northeastward more than a hundred miles, 
chiefly on the southeastern shore, to opposite the mouth of the Sag- 
uenay . 2 But the descriptions of these beds containing shells and 
boulders on the Saint Lawrence indicate that they were mostly, 
if not altogether, deposited by water with floating ice during the 
recession of the ice-sheet, while these marine shells lived where they 
are now found, being thus comparable with the fossiliferous boulder- 
bearing brick-clay of Paisley, Scotland . 3 In the modified drift 
forming Cape Cod, derived from the melting ice-sheet in which it 
had been contained, I collected ten years ago fragments represent- 
ing sixteen species of shells, all now living, eight of which also 
appear iii the foregoing list . 4 
Looking over the various lists of Pleistocene fossils found on 
Gardiner’s island and in Sankoty Head under the drift of the last 
ice-sheet, in these drumlins of till near Boston, and in the modi- 
fied drift of the glacial recession thence northward to Maine, New 
Brunswick, and the valley of the Saint Lawrence, we cannot fail to 
be surprised that all these species are still living in the adjoining 
ocean to-day. So recent was the glacial period 5 that none of them 
has become extinct, nor, with very rare exceptions, undergone any 
1 Bulletin de la Societe Geologique de France, second Series, vol. v, 1847, pp. 89, 
90; Quart. Journ. Geol. Soc., vol. v, p. 343; Am. Journ. Sci., II, vol. xiv, 1852, p. 51. 
2 J. W. Dawson’s Notes on the Post-pliocene Geology of Canada, 1872, pp. 7, 45, 
and 50-53. 
3 T. F. Jamieson in Quart. Journ. Geol. Soc., vol. xxi, 1865, pp. 175-177. 
4 American Naturalist, vol. xiii, 1879, p. 560. 
6 Compare Proceedings of this Society, vol. xxiii, 1888, p. 446. 
