162 University Geological Survey of Kansas. 



Pleurophorus tropidophorus. Plate XX, fig. 7. 



Pleurophorus tropido2)horus Meek, Geol. Surv. Ohio, n, Pal., p. 338, 

 pi. xix, ff. 10a, b, (1875). 



Original description : " Shell transversely oblong, much com- 

 pressed, with . length a little greater than twice the height; 

 posterior margin flattened and bifurcated, the lower truncation 

 being nearly vertical, and the upper sloping obliquely down- 

 ward and backward from the hinder end of the hinge ; cardinal 

 margin straight, equaling about two-thirds the length of the 

 valves ; anterior rounded below and sloping abruptly forward 

 from the beaks above ; basal margin long, parallel to the hinge, 

 nearly straight for most of its length, or faintly sinuous near 

 the middle, rounding up anteriorly, and forming a more or less 

 defined angle at its connection with the lower part of the pos- 

 terior margin behind ; posterior umbonal slope distinctly an- 

 gular from the beaks to the angular posterior basal extremity, 

 while a second carina passes obliquely backward and downward 

 along the middle of the dorsal space above the umbonal ridge 

 of each valve ; beaks depressed to the line of the cardinal 

 margin, very little projecting, and placed one-fifth to one-fourth 

 the length of the valves from the anterior margin. Surface 

 marked by distinct concentric lines of growth, that become 

 strongly defined on the flanks and anterior parts of the valves, 

 but are less distinct on the space above and behind the umbonal 

 angles. Length, 1.10 inches ; height, 0.52 inch ; convexity, 

 about 0.20 inch." 



Range and distribution : Upper Coal Measures ; Kansas 

 City, Mo. 



Pleurophorus costatus. 



Area eostata Brown, Trans. Man. Geol. Soc, i, p. 32, pi. vi, ff. 34, 35, 



(1841). 

 Pleurophorus costatus Brown, King, Cat., p. 11, (1848): King, Mon. 



Perm. Foss. Eng., p. 181, pi. xv, ff. 13, 14, (1850). 

 Pleurophorus eostatiformis Meek and Worthen, Geol. Surv. 111., in, p. 



535, pi. xix, f. 8, and text fig., (1868). 



Meek and Worthen's description : " Shell elongate, suboval, 

 moderately convex, slightly arcuate ; tl^e dorsal and ventral 

 margins rather long, and more or less nearly parallel, the 



