of Wisconsin and Lake Superior. 227 
gradual passage into an overlying conglomerate, which, in turn, 
assumes, above, the characteristics of the Potsdam sandstone. 
Both insist on the absolute continuity and conformability of the 
quartzite, conglomerate and sandstone. Mr. Wood says: “It 
is in the northern slope of the main ridge (on the east of the 
lake) that I found these fossils. If the sandstone containin 
them shall be called ‘ Potsdam,’ and the main ridge ‘ Quartzite, 
then I should say that they were a continuous deposit; and I 
do not know of any reason for separating them, only that they 
differ in hardness; while it is only at the extremes of the scale 
that this difference is manifest.” Prof. Hall states (Geol. Rep, 
quartzite is superimposed a little farther south, by the outliers 
of the Calciferous sandrock, this fact would give countenance to 
the alternative suggested. 
ScoLiTrHuS LINEARIS. 
S. linearis Hall. is present in abundance in some of the frag- 
ments, in the foretF abe t, cylindrical, nest-like cay ay 
or three inches long, extending vertically to the planes 0 |. 
ding. They vary from ‘05 to ‘27 of an inch in diameter. 
