JS^orfh America)) I))te)'(/lacial Deposits. — Upha))). 291 
thick Scarboro' stratified beds were evidently amassed as a 
delta, probably too in a lake of gradually rising level, and the 
origin of so large a supply of sediments seems referable only 
to their derivation chiefly from englacial drift exposed by 
ablation on the margin of ice-fields within the drainage area 
of the delta-forming streams. In this tract of confluence be- 
tween the great eastern and central lobes of the Laurentide ice- 
sheet, represented by the angle of the drift boundary at Sala- 
manca in southwestern New York (plate X), there undoubt- 
edly was brought an exceptional volume of the englacial drift 
by the confluent glacial currents. 
]SFew Engla))d and Xe))' D)-unsv)cl\ — In all the region east- 
ward from Toronto fossiliferous beds recording glacial oscil- 
lations are known to me only in southeastern New Hampshire, 
a few miles back from the present seashore, where white pine 
trees grew and bore cones, and the common marine mussel 
{3fyt)l))s edalis) existed, close to the waning border of the 
ice-sheet, which made a short readvance covering these fos- 
sils;* and in the neighborhood of St. John, N. B., on the 
shore of the Bay of Fundy, where Chalmers describes alterna- 
ting deposits of unstratified boulder-clay, or till, and stratified 
clay with a few pebbles and boulders, both occasionally con- 
taining Yoldia arctica in abundance, while several other spe- 
cies of shells are less frequent or rare.f 
Chalmers shows that the St. John interglacial beds were 
formed at or near the margin of the ice-sheet, and beneath 
the level of the sea, when the land relativel}^ stood 100 to 200 
feet or more below its present hight. Several times of local 
retreat and readvance of the ice-front are clearly indicated. 
The shells of the stratified portions are in situ, but the till en- 
closes littoral species which were probably pushed forward by 
the ice and mingled with the deep-water forms. All the spe- 
cies belong to the present arctic or subarctic marine fauna, 
and this Yoldia, now restricted to polar seas, thrives especial- 
ly near the mouths of muddy streams flowing from glaciers. 
In the till of drumlins near Boston Prof. W. O. Crosb}^ and 
Miss Hetty O. Ballard have very recently noted rare glaciated 
*Warren Upham, Geoli)gy of N. H., vol. iii, 1878, part in, p. 1G3. 
fBulletiii, Geol. Society of America, vol. iv, ISIKI, jip. 3(il-370. 
