Huntingdon Counties, Central Pennsylvania. 525 



Devonian instead of in the top of the Hamilton, as placed 

 in the section. 



The name Reedsville was introduced by Ulrich (Revi- 

 sion). The formation corresponds about to the upper 

 half of the Martinsburg shale. The top sandstone 

 member, with Orthorhyncula, etc., is 30 to 56 feet thick, 

 and extends without change from central Pennsylvania 

 to New River, Ya. Orthorhyncula was found also at Gate 

 City, Va., near the Tennessee line. It is an extremely 

 valuable horizon marker. 



The Trenton limestone here is said to agree well in 

 character with the Trenton nearer its type locality. 



The Rodman limestone is new and is named from Rod- 

 man, a station on the Pennsylvania Railroad near Roar- 

 ing Spring, several miles south of Hollidaysburg, Blair 

 County. This formation is only about 30 feet thick but 

 is persistent throughout Nittany Valley and is identical 

 in character and thickness in Center County and in Blair 

 County. It can be seen in any of the quarries of the 

 region, where it immediately overlies the quarry rock 

 from which it can easily be distinguished by its litho- 

 logic character and by the fact that it outcrops at the 

 top margin of the quarries on the side toward the dip. 

 The Rodman carries a considerable and an interesting 

 assemblage of fossils which may be listed in a future 

 paper. Echinosphserites occurs in a zone of beds at Belle- 

 fonte, Pa., between the Lowville and Trenton, of identical 

 character and in part at least contemporaneous with the 

 Rodman. Ulrich regards the beds in this zone as upper 

 Black River and as falling within the scope of the 

 Chambersburg limestone as denned in the Mercersburg- 

 Chambersburg folio. It is not yet decided whether this 

 Echinosphserites zone is to be identified with the upper or 

 the lower of the two Echinosphserites zones of that region 

 but Ulrich is at present inclined to identify it with the 

 lower. The fauna of the Rodman is not the same as that 

 of the Sinuites bed in the base of which is the upper 

 occurrence of Echinosphaerites, while it contains forms 

 that are so far known only in the lower Echinosphaerites 

 zone. In the complete section these two zones are sep- 

 arated by almost 400 feet of limestone. 



Ulrich thinks the Rodman may be the same as the 

 Niskey limestone of Wherry, in the Lehigh Valley, but in 



