296 PALAEONTOLOGY OF OHIO. 



fcerior ear of the flat ri^ht valve, where it is usually deep and angular 

 in species of this genus, while in the left it is deeper and more angular, 

 though none of the specimens are in a condition to show clearly its exact 

 form. One cast shows a little of the cardinal plate, which is rather 

 coarsely striated longitudinally. None of the specimens of the left 

 valve have the surface well enough preserved to show whether the 

 sharply elevated concentric lines or laminse are minutely waved, as in 

 the other valve, but they probably are so when the surface has not been 

 worn or exfoliated. 



I am not acquainted with any described species so nearly allied to this 

 as to render a comparison necessary. 



Locality and position : Sciotoville, Ohio. Upper part of the Waverly series of the 

 Lower Carboniferous. 



AvicuLOPECTEN WiNCHELLi, Meek. 



Plate 15, figs. 5a and 56 f 



Shell attaining about a medium size ; left valve compressed convex, 

 exclusive of the ears, presenting a slightly oblique, irregularly subtrig- 

 onal or subcircular outline ; hinge equaling two-thirds to three-fourths 

 the greatest breadth below ; basal outline forming a more or less oblique 

 semicircular curve ; posterior margin most prominent near the middle, 

 where it is usually subangular, and thence rounding into the base below, 

 while above it is straightened or even slightly concave in outline 

 obliquely forward and upward into the sinus under the ear; anterior 

 margin most prominent above the middle, where it is somewhat abruptly 

 rounded, and thence descending and curving nearly vertically into the 

 base, and rounding, with a slightly straightened outline, obliquely up- 

 ward and backward into the sinus above ; ears subequal, or with the pos- 

 terior one about one-fourth larger than the other, both abruptly flattened 

 from the umbonal slopes, triangular in form, and shorter than the mar- 

 gins below, the posterior one being generally rather acutely angular, and 

 defined by a deep, wide, rounded or subangular sinus, while the anterior 

 is a little more obtuse than the other, and defined by a somewhat nar- 

 rower and more angular sinus ; beak rather compressed, abruptly pointed, 

 with apex subcentral, and extending to, or very slightly above, the 

 hinge margin. Surface of both disc and ears ornamented by numerous 

 small radiating linear costse or raised striae, about every third, fourth, or 

 fifth one of which is usually slightly larger than others, the smaller 



