46 NEW YORK STATE MUSEUM 



west side of the Adirondack plateau. It extends in the Mohawk valley 

 only as far east as Rome. 



The Frankfort shale is apparently absent in the Champlain basin, but 

 forms south of it a belt that crosses the Mohawk river at its mouth and 

 thence extends westward on the south side of the Mohawk valley ; and 

 southward, disappearing under the Helderbergs but probably reappearing 

 in the southern continuation of the Appalachian slate belt in New Jersey 

 and Pennsylvania. From this distribution of the rocks the inference would 

 suggest itself that the region east of the Adirondacks had become drained 

 during Frankfort time, and the former marine connection of the Appalachian 

 trough and western sea with the Atlantic basin had been interrupted there, 

 the sea gradually withdrawing until at the beginning of Lorraine time it 

 extended only as far as Rome. But it is quite as possible that the Frank- 

 fort beds of the Champlain region, being the last deposited and not pro- 

 tected by being infolded with the other rocks as in Saratoga and Albany 

 counties, have all been abraded again. This view finds support in the fact 

 of the presence of Lorraine beds directly north of the Champlain basin, 

 south of Montreal, with a thickness of several hundred feet and a char- 

 acteristic fauna \_see Ami, 1900, p. 159], and in the great thickness of the 

 formation in Albany and Schenectady counties. 



5 Zone of Dicellograptus complanatus Lapw. 



Dr Ulrich's collection from Indian Territory contains a small graptolite 

 faunule. It was obtained in the Sylvan shale of the Arbuckle mountains, 

 and consists of 



Dicellograptus cf. complanatus Lapworth Climacograptus mississippiensis nov. 

 Diplograptus crassitestus nov. 



Dr Ulrich informs me that this interesting association overlies a Rich- 

 mond fauna. It is hence probably representative of the youngest Lower 

 Siluric beds of North America. This inference is to some extent borne out 

 by the graptolitic evidence, notably by the presence of specimens of a Dicel- 

 lograptus which, as far as their somewhat fragmentary character permits 



