THE NORM AN SKILL GRAPTOLITE FAUNA 277 



a conglomerate at the base of the Lowville (Birdseye), separating 

 it from the Chazy, which is in many respects Hke the Rysedorph 

 conglomerate, but not in fossil content. While not essential to the 

 points involved in this note, yet, for the sake of clearness, a brief 

 description of it will be given when that point is reached in de- 

 scribing the section. 



The mass of the Athens shale (Normanskill) dips at an angle of 

 70° S., and is about 550 feet thick. It occupies the center of 

 Catawba Valley, which structurally is anticlinal, and through which 

 meanders Catawba Creek. The shales where exposed in bluffs 

 weather into thinly cleaved plates or leaves of a dark peppery gray 

 on which the graptolites are not readily observed. The completely 

 weathered soil is ocherous yellow, due to the presence of iron in 

 the original rock. The fossils are in places preserved in pyrite, and 

 as a rule where the seams open upon weathering the surface is 

 rusty. On such surfaces the black fossils stand out clearly. The 

 formation maintains its general character throughout, and termi- 

 nates abruptly against the underlying Black River limestone, and 

 does not here rest upon lower Trenton limestone. In this respect 

 its position differs from the Normanskill of New York, for Ruede- 

 mann states in his summary that these shales rest on lower Trenton 

 limestones. Mather, however,^ in describing the Black River, in 

 which is included the Lowville, several times states that the Black 

 River is underlaid by a brecciated limestone and overlaid by slates. 

 It would appear, therefore, that in certain localities, at least in New 

 York, the succession of strata for this part of the Ordovician is the 

 same as in Virginia; for these Black River limestones and slates 

 of which Mather writes occur at Mount Moreno, and Mount 

 Moreno is one of the four typical locaHties where complete or 

 nearly complete Normanskill faunas have been collected. The 

 conclusion to be drawn from the above is that the Normanskill 

 there rests on Black River limestone as in Virginia. 



The question has also arisen whether the Normanskill is a dis- 

 tinct development of the Ordovician or only a clastic phase of the 

 Trenton. For this locality at least, it would appear to represent 

 a distinct epoch in the Ordovician; for the formation is at least 



"■Nat. Hist. N.Y., Part IV, "Geology," pp. 405-6. 



