ICE WORK IN SOUTHEASTERN MICHIGAN 205 
Associated with this late Wisconsin glaciation, but slightly 
later and cutting across it some 18° further to the west, as 
though made by a slight advance of the ice, is an erosion feature 
not known to have been previously noted. This is to be seen at 
the southwestern corner of the quarry, where it will be destroyed 
in a few more months, as the quarry is being extended in that 
direction. This consists of patches of miniature rock basins and 
narrow grooves, crowded together, in approximately parallel 
positions and covering some three. to four square yards, so far 
as at present exposed. The limestone here is shattered, but 
essentially homogeneous, and has the appearance of a pavement 
formed of irregular blocks with edges rounded. The patches of 
basins are more conspicuous upon those blocks which are slightly 
higher than their neighbors and are better defined toward the 
stoss side of the blocks. It was found impracticable to get the 
basins to show satisfactorily in a field photograph, in which the 
lighting could not be controlled, so plaster casts were made of 
a number of patches for detailed study. Fig. 5 gives a reduced 
view of a cast, with the mold from which it was made at the left. 
The basins are typically of a more or less elongated elliptical 
shape, sharply outlined, rather shallow and have the steepest 
slope toward the iceward side. The distal sides of the basins 
show a more gradual slope up to the general rock surface. The 
deepest part of the basin is either at the center, or placed nearer 
the iceward end, as is the case with the larger rock-basins of 
heavily glaciated regions. Some of the basins can be observed 
only with the help of a magnifier, while the largest noted has 
a length of 35™™, a breadth of 15™™ and depth of 2™™. Consid- 
ering those of all sizes they are very numerous and closely 
placed, occasionally overlapping and superposed. The interiors 
of these basins are very generally perfectly smoothed and 
slightly polished, although with a magnifier delicate scratches 
may be detected. Occasionally some are seen which appear 
rough and have a bruised appearance. Some of the basins 
become elongated into U-shaped troughs, which may be either 
straight or curved. In the case of the curved ones the slope is 
