NATURAL SCIENCES OF PIIILADELPIIIA. 61 



mainly casts with some portions of the surface. It is remarkable 

 in having only a comparatively shallow rounded sinus under the 

 anterior ear of the flat right 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 concen- 

 tric lines or laminae 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 

 Waverley series of the lower Carboniferous. 



AVICULOPECTEN (STEEBLOPTERIA ?) HERTZERI, Meek. 



Shell usually under medium size, higher than wide, ratlier 

 compressed, the right valve being nearly flat, and the left only 

 moderately convex; subovate in general outline (exclusive of the 

 small ears), with a slight backward obliquity caused by the greater 

 prominence of the anterior margin ; basal outline semicircular and 

 curved regularly into the rather prominently rounded anterior 

 side ; posterior margin less prominent than the anterior, and 

 forming a longer and more gentle curve from the posterior ear 

 into the base. Hinge distinctly shorter than the antero-posterior 

 diameter of the valves ; posterior ear in both valves very small, 

 flattened, very obtusely angular, much sliorter than the margin 

 below, but well defined from the umbo, and only separated from 

 «4he margin below by a faint sinuosity ; anterior ear of each valve 

 distinctly larger than the posterior, though not as prominent 

 as the anterior margin below, rather strongly compressed or 

 flattened so as to be abruptly distinct from the umbo, and 

 defined by a distinct sinus from the margin below, the sinus 

 being deeper and more angular in the right valve ; beaks com- 

 pressed, scarcely projecting above the cardinal margin, and 

 placed a little behind the middle of the hinge, as well as that of 

 the valves. Surface of both valves elegantl^^ ornamented by nu- 

 merous, sometimes sharply elevated, nearly equal, very regularly 

 1871.] 



