Bekdk.| Carl W Invertebrate*. 171 



of the usual minute surface granules appear to be visible in 

 some of the molds left in the matrix. Length, about 1.20 

 inch ; height. 0.53 inch ; convexity. 0.44 inch." 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Lawrence, Topeka. 



This species may be easily distinguished by its large, even, 

 sharply elevated ribs and the radiating costa* on the upper pos- 

 terior portion, as well as its long, graceful shape. 



SEDGWICKIA. 



McCoy, Synop. Carb. Fos~. Ireland, p. 61 i IM4 ). 



Sedgwickia topekaens\s. Plate XX, fig. 3. 



Leptodomus topeka* nsis Shurnard, Trans. St. L. Acad. Sci., i, p. 208. 

 ?< dgurickia topekaen&is? Meek and HavdeD, Pal. Upp. Mo., p. 40, 



A. B. 1864). 

 AUorisma iopekaensis Keyes, Geol. Surv. Mo., v, p. 128. 



Meek and Hayden's description : " Shell depressed subovate, 

 about twice as long as high, extremely thin and fragile, gib- 

 bous in the region of the beaks and along the oblique umbonal 

 slopes. Sides flattened above, and becoming a little concave 

 towards the base in front of the middle. Dorsal border nearly 

 horizontal, and slightly concave in outline behind the beak-, 

 where its inflected edge is margined by a rather distinct ridge : 

 ventral border presenting a broad semiovate outline, excepting 

 a very slight sinuosity just in advance of the middle — round- 

 ing up abruptly in front and more gradually behind ; anterior 

 side prominent, gibbous, and narrowly rounded below, obliquely 

 truncated above; posterior side compressed, narrowed, and 

 apparently subtruncate and somewhat gaping at the extremity. 

 Lunular impression in front of the beaks i in casts) moderately 

 distinct, defined by a faintly impressed line. Beaks prominent, 

 gibbous, a little flattened, incurved, and placed between the 

 middle and the anterior extremity, but nearer the former. En- 

 tire surface, in well-preserved specimens, closely covered with 

 minute granules arranged in radiating rows : and ornamented 

 with small concentric ridges, which are almost regular and dis- 

 tinct on the umbones, and end abruptly along an impressed 

 line extending from the posterior side of each beak obliquely 



