366 C. L. Fenton — The Hackberry Stage of 



ments of limestone from the Idiostroma zone. At the 

 Owen Grove quarry the Idiostroma beds are to be seen 

 in the bed of a little creek, and it is to be f onnd also at 

 Rockwell and other points. Besides the stromatoporoids 

 it contains Westemia crassa "Webber, W. gigantea Web- 

 ster, and a large Orthoceras. 



B, IV. The Naticopsis Zone. 



The type locality for the Idiostroma zone is also the 

 type locality for this stage, Hackberry Grove; the type 

 locality for the Naticopsis zone and the rocks above it is 

 the Owen Grove qnarry, near Owen Creek, in Portland 

 Township. At this point there are about thirty feet of 

 brown or dark buff magnesian shales, limestones and 

 argillaceous dolomitic rocks lying immediately above the 

 Idiostroma beds and which are here referred to as the 

 Naticopsis zone. These rocks are very fossiliferous, 

 containing many of the species of the Spirifer zone, as 

 well as the Cyrtoceras sp., the three described species of 

 Westernia, and numerous unidentified gastropods. The 

 chief distinguishing feature of the zone are the gastro- 

 pods, and among these the species Naticopsis gigantea. 



B, V. The Acervularia Zone. 



Overlying the Naticopsis zone at the Owen Grove quarry 

 are some twenty feet bearing numerous fragments of 

 limestone in which are many specimens of a species of 

 Acervularia that has been variously referred to A. pro- 

 funda, A. inequalis and A. davidsoni, but which is now 

 generally considered to be undescribed. This limestone 

 is originally very hard, but on weathering it becomes 

 comparatively soft and easily broken; the color is a 

 whitish gray. It is in place, with poor exposure, near 

 Hackberry Grove, and in the bed of Hackberry Creek are 

 many fossils and fragments from it. The predominat- 

 ing feature of the zone is the corals; the undescribed 

 Acervularia may be found in large numbers and nu- 

 merous varietal forms. There are also Chonophyllum, 

 Cystiphyllum (?), Strombodes, Alveolites, Aulopora, 

 two new species of Heliophyllum and at least two 

 described and two undescribed species of Pachyphyllum. 

 There are also several undetermined species of gastro- 

 pods and pelecypods, though brachiopods are quite 

 uncommon. This zone, with a probable maximum thick- 



