102 DISCOVERY OF FOSSILIFEROUS STRATA OF THE 
3. Lower Cambrian—Known as the Georgia Group, the 
Olenellus Group, &c.; the strata containing Olenel- 
lus trilobites. 
Until very recently, Mr. Walcott, and Mr. 8. W. Ford, 
- who is high authority 1n regard to Cambrian strata, had 
considered the ‘‘ Georgia Group”’ to be the Middle Cam- 
brian, and the Paradoxides beds the Lower Cambrian, in 
direct opposition to the views of the eminent Swedish 
authorities; but lately Mr. Walcott has discovered evi- 
dence which has conrpelled him for himself and others 
to reverse this opinion, and come into harmony with the 
Swedish views. 
Under this subdivision of the Cambrian, each member 
is characterized by a prevailing trilobitic type—the Up- 
per, by the Dicellocephalus ; the Middle, by the Para- 
doxides; the Lower, by the Olenellus. These trilobitic 
names may be used as convenient designations for the re- 
spective subdivisions. 
It must be noted, however, that while this is a conve- 
vient ‘‘working’’ subdivision, it is not at all certain, as 
yet, that it is in all respects a valid one ; for it is not yet 
fully established that the Lower and Middle Cambrian 
are entirely distinct groups in chronological sequence. 
In fact, some indications have been found of the possible 
mingling of their fossils. It may prove that the differ- 
ence in their fauna is one of sedimentation rather than 
of epoch. But until this should be proved, it seems 
more proper to give them the chronological order above 
indicated. 
DISCOVERY OF FOSSILIFEROUS STRATA OF THE MIDDLE 
CAMBRIAN, AT STISSING, N. Y. 
BY WILLIAM B. DWIGHT. 
My field work in Dutchess County since the early part 
of 1886 has shown the presence of very extensive strata 
52 
