Upham.] 
306 
[Nov. 4, 
tinuation of a new park of the city of Boston, encountered a 
fossiliferous clayey stratum a few feet thick, lying near the pres- 
ent level of low tide, underlain by stratified clay, and directly 
overlain by a bed of peat about one foot thick, which is succeeded 
by the latest fine muddy alluvium of this stream, from five to 
twelve feet in thickness. In the upper part of the clay, the thir- 
teen species noted by asterisks in the first column of the following 
table were found, occurring in abundance together, except that 
the oysters were restricted chiefly to one place. 
2. In the dredging of the Charles River during the construc- 
tion of the new bridge from the Back Bay district of Boston to 
Cambridgeport, at a distance about one and a half miles west of 
the State House, there were brought up first river mud, which had a 
thickness of several feet, and next sand containing shells of twelve 
species noted in the second column of the table. The river here 
is a broad tidal estuary, a great part of which has been filled and 
now constitutes the Back Bay district ; and the ground where 
these fossils were dredged forms part of the deepest channel of 
this bay or enlargement of the Charles River back of the original 
peninsula of Boston. The fossiliferous sand was ten feet or more 
below mean low tide level, above which the mean height of the 
tide, both in the Charles River and in Boston Harbor, is ten 
feet. 
The most abundant species here, occurring in great numbers 
and of large size, are My a arenaria , Venus mercenaria , Pecten 
irradians , and Ostrea virginiana. Some of the shells of the long 
clam (Mya) measure five inches in length and three inches in 
width. A small oyster shell in this bed is exceptional, the usual 
length being eight inches, with a width of from two to three 
inches ; while many are ten inches long, and one valve has a thick- 
ness of one and a half inches. 
3. At City Point, the eastern extremity of South Boston, dredg- 
ing is in progress for deepening an adjacent part of the harbor, 
and the mud and sand thus removed are used in the extension of 
City Point for the site of the Marine Park. The depth of water 
where the dredging is being done, midway between the Point and 
Castle Island, is about ten feet below mean low tide, and the ex- 
cavation goes several feet lower, bringing up an abundance of 
fossil shells. Twenty-one species, noted in the third column, 
have been identified here. 
