Maryland Gkological Survey 699 



and interrupted on tlie outer half; the median line of the volution being 

 marked by a row of depressed nodes, which become obsolete toward and 

 upon the chamber of habitation. The intermediate spaces are essentially 

 smooth, or marked only by a peculiar pitted or indented surface, which 

 has not been identified with any external marking." Hall, 1879. 



The specimens found in Maryland consist of parts of a volution which 

 appear to be coiled in one plane. They are referred tentatively to Sand- 

 bergeroceras chemung crisis of the Chemung of New York. More perfect 

 material is needed to permit confident identification. 



Occxirrence. — Jennings Formation, Parkhead Member. Williams 

 Road, on Polish Mountain, 1289; 4 miles southeast of Pratt. 



Collection. — Maryland Geological Survey. 



ARTHROPODA 



Class CRUSTACEA 



Subclass TRILOBITA 



Order PROPARIA 

 Family PHACOPIDAE 



Genus PHACOPS Emmrich 



Phacops RANA (Green)' 



Plate LXXII, Fig. 8 



Description. — Several well-preserved pygidia of this recurrent Ham- 

 ilton species have been found in the Parkhead of Maryland. 



Occurrence. — Jennings Formation, Parkhead Member. Williams 

 Road, on Polish Mountain, 1660; National Road, on Polish Mountain, 

 1625; 21/4 miles above mouth of Sideling Hill Creek; road leading north- 

 east from Pratt, 14 mile west of Fifteenmile Creek. 



Collection. — Maryland Geological Survey. 



' For synonymy and description see page 329. 



