PALEOZOIC TIME — UPPER SILURIAN. 



559 



805-806. 



The Lower Pentamerus limestone, Delthyris Shaly limestone, Encrinal 

 limestone, and Upper Pentamerus occur in eastern New York. The upper 

 two of these subdivisions are quite distinct in eastern New York, though 

 not separable in the center of the State. They thin out in Cayuga County. 



In the Arctic regions, Kennedy Channel, latitude 79°-80°, fossils were 

 obtained by Dr. Hayes, which, according to Meek {J. Sc, I860), closely re- 

 semble those of the Shaly limestone of the Lower Helderberg of New York. 



LowEK Helderberg. — The Lower Pentamerus limestone, overlying the Water-lime, 

 to the eastward, is compact, and mostly in thick layers and about 50' thick. The Catskill 

 or Delthyris Shaly limestone (No. 3) consists of shale and impure thin-bedded limestone. 

 An upper part of the formation was called the Scutella limestone by Vanuxem in his 

 Annual New York Report, the Scutella referred to being the discoidal basal plate of an 

 Encrinite. A bed of limestone corresponding to these two divisions, but without the sub- 

 division, has a thickness of 65' on Cayuga Lake. 



Part of the so-called Upper Pentamerus of eastern New York, in the Hudson valley, 

 according to recent observations of C. E. Beecher, fails of the characteristic fossils of the 

 group, and is referred by him to the lower Oriskany ; it includes the impure limestones 

 above the Encrinal limestone at Becrafts Mountain, near Catskill, and southward. The 

 Upper Pentamerus is distinct at Schoharie and westward nearly to the center of the state, 

 where all the subdivisions of the period merge together. 



Becrafts Mountain, two miles east of the Hudson, near Hudson, consists below (1) of 

 a thin bed of the Tentaculite limestone of the Water-lime ; (2) Lower Pentamerus, 40' 

 to 50' ; (3) Shaly limestone, 50' to 60' ; (4) Encrinal limestone, 40' 

 to 50'. Over these occur the Oriskany sandstone and the Cauda- 

 galli grit. 



In west Tennessee, light-blue limestones of this period, abound- 

 ing in fossils, occur in Hardin, Henry, Denton, Decatur, and Stewart 

 counties. The maximum thickness is about 100'. In southern Illi- 

 nois there are beds of siliceous limestone underlying the Clear Creek 

 limestone, the lower part of which Worthen refers to this period. 

 They rest directly upon limestones o'f the Cincinnati or Hudson 

 age (the Cape Girardeau limestone of the Missouri Report), no 

 Niagara limestone intervening (Worthen). 



In the Appalachian region in Pennsylvania, the Lower Helder- 

 berg, consisting also of impure limestones, has a thickness of 100' 

 or more in the middle belt, and 200' to 250' in the southeastern, 

 which thickness is maintained along the Appalachian chain 

 (Rogers) . 



In the Eastern Border region, at Pembroke, Me., slates and 

 hard sandstones occur with many fossils. In northern Maine the 

 rock is limestone ; and to the north they have great thickness, 

 about Lake Temiscouata, and include both Niagara and Lower 

 Helderberg (L. W. Bailey). The formation extends northeastward 

 to Cape Gaspe, where there are 2000' of limestones, the larger part 

 referred to the Lower Helderberg by Logan, with the upper beds 

 probably Oriskany. They also stretch southwestward toward New 

 Hampshire, in the line of the Gaspe- Worcester trough. 



At Arisaig, in northern Nova Scotia, the Lower Helderberg 

 beds have a thickness of 1040', and overlie nearly 1293' of Niagara, 500' of Clinton, 

 and 180' of Medina beds (H. Eletcher, in an extended report on Nova Scotia, in Eep. 

 Can., 1886). 



805 



Cystideans. — Fig. 805, 

 Apiocystites Gebhardi, 

 from Hall; 806, Ano- 

 malocystites cornutus, 

 from Meek. 



