120 University Geological Survey of Kansas. 



face of the shell ornamented by about twenty-three radiating 

 costa?, each consisting of three to five striae, which extend nearly 

 to the beak ; these bundles are separated by rather broad depres- 

 sions or grooves. There are fine crowded lines of growth visible ; 

 they are prominent on the margins of large specimens as lam- 

 ellar striae. The anterior ear is ornamented by ten to fifteen 

 simple radiating strife and concentric lines of growth ; the 

 posterior ear is similarly marked, except that the radiating lines 

 are fewer and less distinct. Measurements : Height, 69 mm. ; 

 length, 64 mm. ; length of hinge, 40 mm. ; convexity, 12 mm. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Turner. 



The truncation of the posterior side, nature of the fascicles, 

 ears and the general appearance of this shell are so similar to A . 

 providencesis of Cox that I do not hesitate to refer it to that 

 species. Worthen evidently considered it as belonging to that 

 species, for he borrowed a fine specimen from Mr. W. J. Parrish, 

 of Kansas City, to figure, in the volume above referred to, for 

 comparison, with his new species which he named A. chesterensis. 

 Mr. Parrish, so he informs me, collected the specimens figured 

 by Worthen from the Kansas City rocks. Some of our speci- 

 mens are from the same locality. It is therefore probable that 

 they are the same as Keyes's A . fasciculatus , which also is from 

 Kansas City. Keyes, in his diagnosis, gives no characters 

 which distinguish his species from that of Cox. It differs from 

 Worthen's species in the larger fascicles and the truncated 

 upper posterior extremity of the outline, as well as having a 

 comparatively longer hinge. Our specimens are also much 

 more convex than those of A. chesterensis. 



The species can be easily separated from the remainder of our 

 Carboniferous species by. its large size and the fasciculation 

 of the strife. 



