574 SYSTEii.vTic Palioxtology — Upper Devoxiax 



Town Creek, 3943 common. Pahkhead JIembku. Eocky Run ; Williams 

 Eoad on Polish Mountain, 16G0. Woodmont Mejeber, Ithaca Fauna. 

 Two miles west of Pawpaw, West Virginia, 1340 abundant, 1388 abun- 

 dant; Little Orleans, 1446; Woodmont, 1032, lOGT common; Hancock, 

 690 abundant; Hancock-Harrisonville IJoad, 726 abundant, 880, 944; 

 Millstone, 1057 ; Berkeley Springs, West Virginia, 786 common, 1058, 

 1080, 1371 ; Yellow Springs, West A'irginia, 734 abundant. 

 Collection. — Maryland Geological Survey. 



SciilZOPIIORIA STRIATULA VAIi. MARYLANDICA n. Var. 



Plate LIU, Figs. 2-9 



Description. — This is a persistently small shell, none of the specimens 

 we have observed attaining the dimensions even of S. propinciua. The 

 largest of these are only about 20 mm. wide while the average s])ecimen 

 in places where they most abound is considerably smaller. 



Ventral valve convex in the umbonal region with erect but not conspicu- 

 ous beak. A median sinus begins on the umbo, widens rapidly, on the 

 margin covering fully one-half the width of the valve, and becomes deeply 

 and distinctly impressed. Hinge-line shorter than one-half the width 

 of the valve. The dorsal valve is full and gibbous at the umbo which 

 projects beyond the short hinge-line with decided concave slopes to the 

 lateral margins. Corresponding to the median depression of the opjiosite 

 valve is a broad, low, very obscure convexity, over which the sparse con- 

 centric growth lines when present make a retral curve, and which is 

 flattened or even depressed and grooved on its summit. This median 

 depression of the valve renders it often of an aspect so similar to that 

 of the ventral valve that it is sometimes difficult to distinguish one from 

 the other. The surface strise vary irregularly in size, are rounded and 

 simple, increasing by intercalation. 



This variety is very well defined and will be recognized by its uni- 

 formly and contrasting small size, broad ventral sinus, obscure and 

 depressed dorsal fold. It is distinguished from the various Devonian 

 representatives of the genus already mentioned by a greater difference 

 than is recognizable between any two of these, but as it occurs in the same 



