98 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
241st MEETING. NovemBeErR 24, 1883. 
Vice-President Brii1nes in the Chair. 
Fifty-three members and guests present. 
It was announced by the Chair that the next meeting would be 
held in the Lecture Hall of the National Museum, that the mem- 
bers of the Anthropological and Biological Societies were invited 
to be present, and that the members of all three societies were re- 
quested to invite their friends. 
Opportunity was afforded for the introduction of amendments to 
the Constitution, but none were offered. 
Mr. C. D. WAtcorr made a communication on 
THE CAMBRIAN SYSTEM IN THE UNITED STATES AND CANADA. 
[Abstract. ] 
Defining the Paleozoic period as has been doné by Geikie in his 
Text-Book of Geology, it will include all the older sedimentary for- 
mations containing organic remains, up to the top of the Permian. 
Upon the paleontologic evidence it may be divided into an “ older 
and newer division, the former (from the base of the Cambrian to 
the top of the Silurian system) distinguished more especially by the 
abundance of its graptolitic, trilobitic, and brachiopodous fauna, 
and by the absence of vertebrate remains ; the latter (from the top 
of the Silurian system to the top of the Permian system) by the 
number and variety of its fishes and amphibians, the disappearance 
of graptolites and trilobites, and the abundance of its cryptogamic 
terrestrial flora.” The two divisions may be still further subdivided ; 
the upper into the Carboniferous and Devonian, the lower into the 
Silurian above and the Cambrian beneath. It is the Cambrian 
division we now have to consider. 
Stratigraphically it is difficult to fix any definite upper limit to 
the Cambrian system, owing to local causes having affected the con- 
ditions of sedimentation and consequent extinction or continuance of 
the fauna. Upon the evidence of the section in New York State on 
the western side of Lake Champlain, the Potsdam sandstone closes 
the period stratigraphically and paleontologically, the Calciferous 
formation forming little more than a closing deposit of the Potsdam; 
and the large Chazy fauna appearing suddenly in the overlying lime- 
stone is entirely distinct from that of the Potsdam. In central 
