OEDOVICIAN FAUNAS IN LAKE CHAMPLAIN VALLEY 461 



ring, as the two trilobites mentioned do on lake Champlain, in association with 

 crinoidal columns of unusually large size, while the trilobites are unusually small. 

 He considers that the admixture of arenaceous matter, while it did not interfere 

 with the production of the species, has diminished their size. 



Conclusions 



Messrs Matthew* and Ruedemannf have traced the Utica as a cold current from 

 Europe invading the warm seas of the Trenton, and passing from the noi'theast 

 around the southern slopes of the Adirondack island. There seems to be evidence 

 pointing to the conclusion that the currents depositing limestone in the clear seas 

 of the earlier period studied in this paper were from southwest to northeast, and 

 that the cui'rents gradually changed to a reverse direction over the soft muds which 

 closed the period. Some of this evidence is found in the thinning of the Birdseye 

 formation in the Champlain valley ; in the luxuriant development of warm water 

 corals and delicate bryozoa ; in the developmental forms of the species common 

 to the central New York and Champlain Trenton on the one hand and the Cham- 

 plain and Canadian Trenton on the other. 



The Black River zones are well marked and characteristic, and differ consider- 

 ably from those of the western New York sections. The group is about 75 feet 

 thick in the southern portion of the region. 



The Trenton carries a very abundant fauna, the species not so strikingly limited 

 to zones as in the adjacent groups, but commingling New York and Canadian types. 

 Its thickness in the region is from 150 to 200 feet. 



The Utica presents at least 475 feet in thickness of shales, carrying a " stunted " 

 fauna for the most pait, but a great variety of linguloid forms. No fossils char- 

 acteristic of any higher formations are found in the region. 



The localities afford a rich paleontological field of investigation and have fur- 

 nished us to date 42 species of brachiopods, 14 of lamellibranchs, 23 of gastropods, 

 9 of cephalopods, and 16 of trilobites. 



Remarks on the paper of Mr White were made by Henry M. Seely, 

 H. P. Gushing, H. M. Ami, C. S. Prosser, the chairman, and the author. 



Discussion 



Dr H. M. Auii pointed out the excellent detailed stratigrapliical as well as 

 paleontological work for the lake Champlain valley. Manj' of the faunal zones 

 and other peculiarities in the stratigraphical column, as pointed out by Doctor 

 White, were identical with their Canadian equivalents. The beds holding Leperditia 

 fabulites band, overlaid by the Columnaria halli, and these in turn capped by a 

 Maclurea limestone, constituting the various members of the Birdseye and Black 

 River formations in the Ottawa Paleozoic basin, agree well, as far as faunal succes- 

 sion and relation and also as regards their origin and lithological characters. 



As regards the Trenton limestone, while the leading forms of fossil organic re- 

 mains were identical, both in the Champlain valley and Ontario, there were a 

 number of interesting points of difference in the vertical range and position as- 

 signed to certain species, as, for example, Trematis oitawaensis. This species is in- 



*G. F. Matthew: Bull. Nat. Hist. Soe. New Brunswick, vol. xi, 1893, pp. 3-18. 

 t R. Ruedemann : American Geologist, vol. xix, 1897, pp. 367-391. 



