Maryland Geological Survey 101 



octocostatus , while Choneies jerseijensis is found in its upper strata at 

 many localities. At Keyser, Camarocrinus stellaius is found in profusion 

 in a thin-bedded shaly limestone just below the Gypidula subzone. A 

 great number of cystids have been obtained in the lower part of this sub- 

 zone, constituting one of the most remarkable features of the entire fauna. 

 These include Jakelocystis harlleyi, J. papillatus, J. avellana. Lepocrinites 

 manlius. Pseudocrinites gordoni, Spliwrocystltes glohularis, S. multi- 

 fasciatus, and Tetracystis chrysalis. 



The Gypidula cocymanensis var. prognoslica Snhzone. — This zone is the 

 most persistent faunal subdivision in the Keyser member. It is found in 

 nearly all the sections exposing its horizon, and is hence of great value for 

 purposes of correlation. It is filled with a great profusion of a small 

 variety of Gypidula, G. cocymanensis var. prognostica, which occurs but 

 rarely at other horizons. 



Bryozoan Suhzone. — The succeeding beds are usually shaly, thin- 

 bedded, and cany a profusion of bryozoa of many species. The Decker 

 Ferry fauna inchiding Choneies jerseycnsis, and Schuchertella declicrensis 

 recurs in it. This was called by Ulrich the Petalotrypa subzone from a 

 characteristic bryozoan since identified as DipJostenopora siluriana by 

 Bassler. 



Favosites HELDERBERGI.E VAR. PR.TiCEDEXs ZoiVE. — The strata abovc 

 the bryozoan subzone contain a fauna which differs in many respects from 

 that beneath and manifests distinct relations to the Coeymans. Few 

 species of brachiopods occur in it and most of these are not found in the 

 lower beds. This zone may be divided into the following subzones: 



Keyser Coral Reef Subzone. — A massive coral reef is found at Keyser. 

 West A'irginia, and at Potomac Station, Marj'Iand, above the bryozoan 

 subzone which abounds in Cyathophyllum schucherli, Favosites helder- 

 bergice var. prcecedens and contains also Haly sites catenulaiu^s. Ulrich 

 also reports Cyathophyllum inequale from this horizon. 



Rensselceria mutabilis Suhzone. — Rensselaria mutahilis is found in pro- 

 fusion at Keyser, Corriganville, and Tonoloway at apparently the same 

 horizon above the Keyser coral subzone. 



