596 IFUIB/RMICAUNS JL JRAMMR CSAIL) 
The basins which occur in broad stream deposits, and which 
have suggested the name “pitted plains” have been confessedly 
difficult of explanation. The notable ones near New Haven 
have been thought to be due to deficient filling, or to whirling 
currents in the river. Professor Woodward informs the writer 
that he is convinced, from his personal examination, that these 
are of ice-block genesis. Such basins have not been often 
observed in New York. The best example that has fallen 
under the writer’s observation les near the village of Tully, 
upon the south, in the gravel plain left by the glacial waters. 
It borders the highway leading from the station and village to 
the Assembly grounds, and is of irregular shape and large 
extent. The most reasonable explanation is that it was the site 
of an isolated mass of ice, but whether buried in the gravel or 
projecting above is not determined, no study of the basin 
having been made. The occurrence further south, in the same 
detrital plain, of numerous lakelets, suggests that there are prob- 
ably many similar basins in the locality. 
SUMMARY. 
The basins in deltas seem to be divisible into two classes: 
(a) Those by ice-block origin, and 
(6) Those by circumdeposition. 
These may be discriminated by the following theoretical 
Characters: 
(a) Shape usually irregular; relatively deep; walls steep; 
material of the walls coarse or even till-like, with possible 
boulders; size, often large; position, often above the water- 
plane. (These characters would be greatly modified in cases 
where the ice-block was wholly buried in the drift.) : 
(0) Position always beneath water-plane, and usually behind a 
bar or embankment; depth relatively small; shape, with smooth 
curving outlines; material of the walls, well assorted and finer 
than the adjacent delta mass. 
HERMAN L. FAIRCHILD. 
