372 SYSTEMATIC PALEONTOLOGY 



Basal margin sigmoidal, the convex portion situated next to the longest 

 lateral face, the concave portion to the shorter, and the shorter lateral 

 margin deflected downwards in some cases (probably the marginal row 

 of plates ) . 



" The surface of the plates is flattened or slightly convex on the sides, 

 and very faintly depressed along the middle, the whole marked by rather 

 closely arranged, annulating, and scaliform transverse lines parallel with 

 the basal or sigmoidal margin, and marking stages of growth. These 

 transverse lines are usually faintest near the apex, and gradually increase 

 in width with the increased growth of the plate, but in some cases they 

 are quite irregular in their distances. 



" The length from the apex to the basal margin of the plate is usually a 

 little greater than the transverse diameter, and seldom exceeds a sixteenth 

 of an inch, the largest specimens seen not measuring a line in their 

 greatest diameter/' Hall and Whitfield, 1875. 



Occurrence. MARTINSBUEG SHALE (Eden division). Jordans Knob, 

 one and one-half miles, northeast of Ft. Lou don; Tuscarora Mountain, 

 two and one-half miles southeast of McConnellsburg, Pennsylvania; and 

 in sandstone debris on the east slopes of Eickard Mountain, Washington 

 County, Maryland. Also in the Corynoides bed at Williamsport, 

 Maryland. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Superorder MALACOSTRACA 



Division PHYLLOCARIDA 



Family CERATIOCARIDAE 



Genus CARYOCARIS Salter 



CAKYOCAEIS SILICULA n. sp. 



Plate LII, Figs. 21-23 



Description. Pod-shaped bodies which have been identified by Salter 

 as the carapace of phyllopods under the name of Caryocaris, are known 

 in the Canadian shales of America, but no more recent species have been 



