3/0 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Fossils. — Palaeontologically, according toVanuxem,this rock divides 

 itself into three parts : — 



1st (from above). Layers with occasional nodules of hornstone. 



2ndly. Similar beds, with Pentamerus galeatus (not the Clinton 

 shell,' which is P. oblongus, p. 356), Euomphalus profundus, and other 

 fossils ; having under them a series of layers with Lepocrinites Geb- 

 hardii. 



3rdly. More layers with Pentamerus galeatus, separated distinctly 

 from those with the Lepocrinites Gebhardii. 



At Schoharie we see only two divisions. 



Mather finds many fossils in this rock ; but he gives but a slender 

 account of them. Of those we know, six are original, five are de- 

 rived from other groups, and three are typical. Twelve only are 

 mentioned. Two Brachiopoda extensively distributed in the Lower 

 Silurian stage are met with here. 



Fossils recurrent in Europe. — These are two, — Avicula naviformis 

 in the Ludlow of Westmoreland (Sharpe) ; and Spirifer plicatus, 

 Wenlock of Shropshire and Ludlow of Westmoreland. 



Fossils recurrent in New York. — Of eight recurrents, four are 

 intimately connected with the Niagara group, and most of the others 

 are found in the neighbouring strata also closely related to the Nia- 

 gara ; so that we may consider, with the lamented Sharpe, that the 

 Pentamerus Limestone and its associated limestones form a Western 

 equivalent of the European Wenlock. 



Further particulars of considerable interest may be seen by con- 

 sulting Table VI. 



Delthyris (Catskill) Shaly Limestone. 



Mineral Character. — According to Hall (Geol. Rep. p. 144), this is 

 an argillaceous shaly mass, or a shale with alternating beds of com- 

 pact limestone. It was named from the Delthyris macropleura of 

 Conrad. 



Mather (p. 344) very properly arranges this limestone in three 

 subdivisions : — 



a. The upper portion, often called " Scutella-limestone," is a 

 coarse, subcrystalline, grey limestone, full of fossils, with some pecu- 

 liar to each stratum. The shallow, almost discoidal pelvis of an En- 

 crinite, like a Scutella, is very abundant. It defines and limits this 

 division. 



b. The middle subdivision is a slaty limestone containing many 

 genera of Testacea, Corals, Encrinites, with some Trilobites. Some 

 species of the Pentamerus are characteristic (Mather, p. 345). 



c. The lower subdivision is a mass of slaty argillo-siliceous lime- 

 stone abounding also in fossil remains, especially in Strophomena. 



Transition. — Linked together with the previous and subsequent 

 group very closely. 



Place. — The upper subdivision (a) is well developed from the west 

 frontier-line of Schoharie County, ranging eastward by Schoharie to 

 the east brow of the Helderberg Mountains, and from thence south- 



