﻿ON SILURIC AND DEVONIC CYSTIDEA AND 

 CAM ^ROCRINUS 



By CHARLES SCHUCHERT 



Introduction 



The Ontaric or Siluric system of eastern United States is termi- 

 nated by the Manlius formation, above which is the Helderbergian 

 group with its prolific fauna so unlike those of older American de- 

 posits. Heretofore the fauna of the Manlius has been regarded as a 

 very small one and is essentially described in three places, by Hall, 1 

 Whitfield, 2 and Grabau. 3 It is now quite evident, however, that this 

 formation has a much more extensive fauna than has been surmised. 4 

 This is true not only for New York west of the Helderberg moun- 

 tains, but especially for Pennsylvania and Maryland. Along the 

 eastern escarpments of the Helderberg mountains these deposits in- 

 clude only the upper half of the beds known farther west and south, 

 and the strata consist of thin-bedded limestones with the fossils either 

 poorly preserved or not separable from the matrix. West of the 

 Helderberg mountains, but more particularly in Pennsylvania and 

 Maryland, considerable beds of shale occur in the lower half of the 

 Manlius, and locally quantities of fossils, especially of bryozoa, are 

 here found. One of the best places in Pennsylvania exposing this 

 formation is at Clark's Mills, near New Bloomfield ; at this locality 

 cystids are rare, but the bryozoa occur abundantly. Near the south- 

 ern border of Pennsylvania Stromatopora is common. About Cum- 

 berland, Maryland, bryozoa and a few species of corals and brachio- 

 pods predominate, and 30 miles to the southwest, near Keyser, West 

 Virginia, cystids, bryozoa, and some forms of brachiopods are the 

 prevailing fossils. 



Owing to extensive alterations and improvements in the road-bed 

 of the Baltimore and Ohio railroad, much ballast has been required, 

 and one of the quarries established for the purpose of obtaining 

 road metal was located near the town of Keyser, West Virginia. It 



l Nat. Hist. N. Y., Pal., in, 1859 [1861]. 

 - Gcol. Surv. Ohio, Geo!., vn, 1893. 



3 Bull. Gcol. Soc. Amer., 11, 1900, pp. 347-376. 



4 Since this was written, Weller has added a number of new species. See 

 Gcol. Sun: New Jersey. Pal., in, 1903. 



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