168 University Geological Survey of Kansas. 



themselves in radiating lines, which are crossed by more or 

 less distinct lines of growth ; on the compressed corselet, above 

 and behind the umbonal carina, there are usually two or more 

 obscure radiating ridges and furrows, crossed by moderately 

 distinct, granular lines of growth, parallel to the truncated 

 posterior margin. Length of the largest example seen, 0.50 

 inch ; height of the umbones in the same, 0.30 inch ; height of 

 the truncated posterior end, same, 0.16 inch ; convexity, about 

 0.13 inch." 



Range and distribution : Upper Coal Measures ; Topeka. 



Allorisma granosum. Plate XX, fig. 10. 



Leptodomus granosus Shumard, Trans. St. L. Acad. Sci., i, p. 207. 

 Allorisma ( Sedgivickia) granosa Meek, Fin. Rep. U. S. Geol. Surv. 



Neb., p. 220, pi. n, f. 8, (1872). 

 Allorisma granosum Keyes, Geol. Surv. Mo., v, p. 128, (1895). 



Meek's description : "Shell very thin, approaching an irregu- 

 lar, oblong form, the length being less than twice the height, 

 very convex, most gibbous part being near the middle of the 

 valves; beaks prominent, incurved, somewhat flattened on the 

 outer side, and placed about half way between the middle and 

 the front. Dorsal margin strise straight behind the beaks and 

 nearly parallel to the general outline of the base, inflected so 

 as to form a distinct, flattened, lanceolate, lunule-like area, 

 bounded on each side by a well-defined subangular ridge ; pos- 

 terior side nearly or quite closed, obliquely truncated, with 

 sometimes a faint sinuosity near the middle ; anterior side 

 rather abruptly sloping forward, and straightened above, and 

 rounding into the base below, near which it seems to be a little 

 gaping ; base somewhat straightened, or even a little sinuous 

 in outline, just in front of the middle, at the termination of a 

 broad, very shallow cavity, extending a little obliquely down- 

 ward and backward from the umbonal region ; behind this rather 

 prominent, thence ascending obliquely, with a slightly convex 

 outline, to the truncated posterior margin. Posterior umbonal 

 slopes very prominently rounded above, and continued as a low 

 undefined ridge, obliquely backward and downward ; posterior 

 dorsal slope, above the umbonal ridge, with an oblique, shal- 



