266 SYSTEMATIC PALEONTOLOGY 



filling the triangular foramen of the dorsal valve; beak uniformly per- 

 forated with a minute circular opening; dorsal valve depressed convex, 

 sometimes more convex in the middle, suddenly deflected near the margin 

 and flattened towards the cardinal line ; ventral valve concave, gradually 

 or sometimes suddenly inflected towards the basal margin ; surface marked 

 by fine rounded radiating striae, which alternate at unequal intervals 

 with coarser ones; striae increasing in number towards the margin of 

 the shell, crossed by fine elevated concentric lines and a few imbricating 

 lines of growth." Hall, 1847. 



This very abundant brachiopod has such a long range that it is of little 

 value for detailed stratigraphic purposes, although it is true that the 

 varieties or mutations of the species which occur at various horizons hold 

 their characters fairly well if minute discriminations are made. The 

 illustrations represent the common Maysville form of the species occur- 

 ring in the Pulaski shale of New York. The same form occurs at the 

 corresponding horizon in Pennsylvania and Maryland. 



Occurrence. MARTINSBURG SHALE (Fairview division). Tuscarora 

 Mountain, one and one-half miles southwest of McConnellsburg, Penn- 

 sylvania. 



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



Genus TRIPLECIA Hall 



TRIPLECIA (CLIFTONIA) SIMULATRIX n. sp. 

 Plate XLIX, Figs. 11-13 



Description. The strata of the Chambersburg limestone succeeding 

 the Lowville division and the Sinuites bed at the base of the Martinsburg 

 shale, contain a radially plicated brachiopod which is so similar to small 

 examples of Platystrophia that its references to that genus would seem 

 proper. However, upon close examination this new species is found to 

 have the characteristic bifurcated cardinal process of Triplecia and to 

 lack the surface granulations of Platystrophia. The open delthyrium of 

 Platystrophia is also absent, but the deltidium of the Strophomenidae 

 is present. 



