950 The American Naturalist. [November,. 
GEOLOGY AND PALEONTOLOGY. 
The Cambrian Rocks of Pennsylvania from the Susque- 
hanna to the Delaware.—Mr. C. D. Walcott has published his 
notes on the basal quartzites and limestones of the lower Paleozoic 
rocks that extend across Pennsylvania, from the Susquehanna river to 
the Delaware river, and across New Jersey to Orange County, New 
York, on the north, and into Chester County, Pennsylvania, on the 
east. The paper is concluded with the following brief summary of the 
results of the author’s observations : 
“ The discovery of the Olenellus or Lower Cambrian fauna in the 
Reading sandstone practically completes the correlation of the South 
mountain, Chickis and Reading quartzites of Pennsylvania, and estab- 
lishes the correctness of the early correlations of McClure, Eaton, 
Emmons and Rogers. They all considered the basal quartzite as the 
same formation from Vermont to Tennessee; and the discoveries of recent. 
years have proven that the basal sandstone of Alabama, Tennesseé 
and Virginia (Chilowee quartzite) ; Maryland, Pennsylvania and New 
Jersey (the Reading quartzite); New York and Vermont (Bennington 
quartzite) ; were all deposited in Lower Cambrian time, and that they 
contain the characteristic Olenellus fauna throughout their geographic 
distribution. "The superjacent limestones carry the Olenellus fauna in 
their lower portions, in northern and southern Vermont, eastern New 
York, New Jersey and Pennsylvania. To the south of Pennsylvania 
the lower portions of the limestones appear to be represented by shales, 
and tbe upper and middle Cambrian faunas are found in the lower 
half of the Knox dolomite series of Tennessee, and they will probably 
be discovered in the same series in Virginia and Maryland, when a 
thorough search is made for them. "The same may be predicted, but 
with less assurance, for the northern belt of limestone crossing Pennsyl- 
vania and into New Jersey, as the limestones between the Olenellus 
zone and the Trenton zone represent the intervals of the middle and 
upper Cambrian and lower Ordovician, or the Caleiferous and Chazy 
zones, of the New York section. The working out of the details of 
this section in southeastern Pennsylvania is an interesting problem, 
left for solution to some geologist who has the necessary paleontologic 
training and who will not be discouraged by the prospect of a good deal 
of hard work before the desired result can be obtained." 
^ Dai ap A LA Nes 
BC DANIE Oe ee 
