305 
fUpham 
1891 .] 
hole is about one-half mile east of the station, and appears to be 
the basin of a waterfall, the stream coming in on the north side 
of the valley. This pot-hole measures 43 feet diameter in one 
direction, and 45 feet in another at right angles to the first. Its 
diameter is a little greater below the rim than at it. At the 
time I visited it (1874) it was nearly full of gravel ; its depth can 
only be surmised. But judging from its great diameter and its 
remarkable evenness, appearing almost as if it turned in lathe, 
it must have considerable depth. 
November 4, 1891. 
President G. L. Goodale in the chair. Seventy-two persons 
present. 
The President announced the death, during the summer vaca- 
tion, of Dr. D. Humphreys Storer and Mr. Edward Burgess. 
The following paper was read : — 
RECENT FOSSILS OF THE HARBOR AND BACK 
BAY, BOSTON. 
BY WARREN EPHAM. 
Fossil marine shells of the Postglacial or Recent epoch have 
been lately discovered at several places in the vicinity of Bos- 
ton. indicating slight postglacial changes in the relative levels of 
land and sea, and proving considerable changes in the tempera- 
ture of the sea here. These fossils have been carefully collected 
and studied by Miss D. L. Bryant, of the class of 1891, Massa- 
chusetts Institute of Technology ; and, with topographic and 
geologic notes of the localities of their occurrence, they were the 
theme of her graduating thesis, to which I am indebted for a 
large share of both the observed^facts and the conclusions drawn 
from them, as here presented. Another interesting collection 
has been made by Mr. Collier Cobb, instructor in geology and 
palaeontology, of the Institute of Technology. Miss Bryant 
gives lists of species obtained by excavations and dredging in 
three localities. 
1. Grading and deep trenches along the valley and estuary of 
Muddy River, adjoining Brookline and forming the western con- 
PROCEEDIX GS B. S. X. H. 
VOL. XXV. 
20 
MARCH, 1892. 
