Bkede.] Carboniferous Invertebrates. 151 



There is a depression on some casts on the anterior side of the 

 umbones extending somewhat below to about the elevation of 

 the upper part of the posterior scar, in front of which is a cor- 

 responding nodose ridge. This character varies greatly in dif- 

 ferent specimens, but the characters are generally sufficiently 

 developed to be detected. In the cast, the beaks are rather 

 widely separated and the top of the cast in front of them is 

 slightly concave, yet nearly flat. 



Range and distribution : Upper Coal Measures; Kansas City, 

 Rosedale, Turner, Topeka, Grand Summit. 



This species may be easily distinguished from the preceding 

 by its larger size, longer shell, and more robust appearance. 



Nucula pulchella. Plate XXI, figs. 5a-c. 



Nucula pulchella Beede and Rogers, Kans. Univ. Quart., vin, p. 132, pi. 

 xxxiv, ff. 5a-c, (1899). 



Original description : " Shell very small, subtrigonal in out- 

 line, ventricose ; anterior border straight, rounding abruptly to 

 the ventral margin, which is rounded ; posterior abruptly trun- 

 cated nearly at right angles with the ventral margin. Beaks 

 prominent, incurved, situated nearly at the posterior end of 

 the shell ; lunule not well defined. The greatest convexity is 

 at the umbo. The surface is ornamented by fine, elevated, 

 concentric stria? and undulations of growth. Length, 44 mm. ; 

 height, 3-2 mm. ; convexity, 3 mm." 



Range and distribution : Upper Coal Measures ; Lawrence. 



This species differs from N. beyrichi in being more triangu- 

 lar, shorter, and the beaks more prominent. It differs from 

 X. ventricosa, also, in the above respects, as well as being very 

 much smaller and having very much more prominent surface 

 markings. 



