68 



SCIENCE 



[N. S. Vol. XLYI. No. 1177 



of sea transgression. The lower fifty feet of 

 this division contains the Protolenus fauna 

 which Walcott interprets as marking the 

 passage beds between Lower and Middle Cam- 

 brian. Above are shales and slates, 200 feet 

 thick, carrying the Paradoxides fauna. The 

 middle division, Johannian, of the St. John 

 group consists of coarse elastics characterized 

 by the presence of Lingulella, while the upper 

 one, Bretonian, is largely dark gray to black 

 shale which is in part of Ordovician age. 



Emphasis is laid upon the complete separa- 

 tion of the Atlantic coastal seas from those 

 of the interior of ISTorth America during early 

 Cambrian time, and " the presence of a deep 

 and broad abyss off the Atlantic coast in this 

 early time " is postulated. 



Ontario.- — The Potsdam sandstones which 

 outcrop in the vicinity of Kingston are de- 

 scribed by M. B. Baker^ in a report which in 



the main treats of pre-Oambrian geology. 

 Two members, a lower buff, and an upper red 

 sandstone, are recognized as forming the 

 Potsdam formation. Both were deposited in 

 the basins and hollows between low rounded 

 hills of pre-Cambrian rock. Basal and other 

 conglomerates are common. Cross-bedding is 

 frequently observed and the strata are non- 

 fossiliferous. The so-called " tree concre- 

 tions " are interpreted as structural accumula- 

 tions resulting from whirlpools and eddies. 



ORDOVICIAN 



Ontario. — ^Possils from the Trenton lime- 

 stone in the the Balsam Lake region are de- 

 scribed by Euedemann.^ A new species of 

 graptolite is referred to the genus Inocaulis. 

 Unusualy well-preserved specimens of Sten- 

 aster salteri confirm the suspicion that this 



Fig. 1. Correlation chart of Ordovician strata in Ontario. Compiled from papers by Foerste, Parks, 



Kindle and Raymond. 



5 M. B. Baker, ' ' The Geology of Kingston and 

 Vicinity, ' ' Ontario Bur. Mines, Ann. Eept., Vol. 25, 

 Pt. 3, pp. 1-36, 1916. 



6 E. Euedemann, ' ' Paleontologie Contributions 

 from the New York State Museum," New York 

 State Mus. BuU. 189, 1916. 



