568 Annals of the Carxegik Museum. 



the Ottawa Valley region the sandstone carries a modified Camarofarhia 

 plena fauna. At the typical sections the Li/i^i^i/la brainerdi faunule is 

 at the base of the formation, while the Caniarota'chia plena fauna 

 comes in 700 feet above the base. 



Since the fullest development of the limestone deposits of this age 

 is found in the region of Chazy and Valcour Island, that region must 

 represent the place in which the Chazy sea persisted longest. From 

 the evidence outlined in the preceding pages, it would seem that in 

 this region there was a shallow sea invading south and west on a slowly 

 sinking land. Since the Chazy fauna seems to be developed less directly 

 from the Beekmantown fauna of the Lake Champlain region than from 

 that of Newfoundland, and since new European types are added to the 

 American fauna during Chazy time, it seems probable that the sea was 

 more constant and open toward the east or northeast. 



If the sea were invading upon the land to the south and west, the 

 sandstone in the Champlain Valley would represent shore conditions, 

 and should be younger in age as it is traced south and west. That 

 this is the case is shown by the faunas. At Valcour Island there were 

 300 feet of rock deposited during Chazy time before the Maclurites 

 inai^nt/s fauna became prominent, while at Crown Point, 40 miles south, 

 this fauna follows immediately upon the sandstone at the base of the 

 section. Evidently during a large part of Chazy time the transgression 

 was southward, but later it began to move westward. The region now 

 occupied by the Ottawa Valley was then invaded, and the sea brought 

 with it a part of the Camarota-chia plena fauna. The date of this in- 

 vasion to the west can be approximated, for in the middle of the sec- 

 tion at L' Original, Caniaro/o'chia plena, Raphistona slaniineiini, and 

 Malocystites viurchisoni are found. At Valcour Island these three 

 species are found together in Zone A.,g, 775 feet above the base, 

 thus showing that the formation in the Ottawa Valley represents 

 only the very latest part of Chazy time. 



Ulrich and Schuchert bring out this idea of a sea invading west- 

 ward and southward in their paper on Paleozoic Seas and Barriers 

 (Report New York State Paleontologist, 1902, page 639). They 

 state: " With the earlier part of the subsidence [the Chazy inva- 

 sion] the Atlantic invaded the continent westward . . . The tyjMcal 

 Chazy formation . . . bears evidence in its members of having en- 

 croached southward and westward in the arms, the latest beds . . . 

 extendintr furthest south and west." 



