Beede.] Carboniferous Invertebrates. 149 



the postero-dorsal margin, their outline, as seen from above, 

 forming an elongate ellipse which has a concave surface on each 

 side of the median ridge, which is formed by the upilexed 

 margins of the valves there: umbones prominent; beaks in- 

 curved, situated about two-fifths the full length of the shell 

 from its front; surface marked by fine, regular, concentric, 

 raised strise, which are obsolete upon the umbonal ridges and 

 the space which they enclose." 



Length of our specimen, 27 mm. ; height, 14 mm. ; con- 

 vexity, 10 mm. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Rosedale, Lawrence, Topeka. 



Nuculana bellistriata attemiata. 



Nuculana bellislriata var. attenuata Meek, Fin. Rep. U. S. Geo!. Surv. 

 Neb., p. '206, pi. x, ff. 11a, b, (1S72). 



Some are inclined to doubt the validity of this variety. There 

 are forms of .V. bellistriata which are more pointed, more finely 

 striated and considerably smaller than others. The striations 

 on this small shell are much smaller, and are separated by much 

 narrower spaces, than the corresponding striae of the umbonal 

 regions of the larger specimens. I believe they are varietally 

 distinct. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Topeka. 



NUCULA. 



Lamarck, Anim. Sans Vert., p. 87, (1S01). 



Nucula beyrichi. Plate XXII, fig. 8. 



X in- hi a beyrichi Geinitz, Carb. u. Dvas in Neb., p. 21, pi. i, if. 3G, 37, 

 (1856); Meek, Fin. Rep. U. S. Geol. Surv. Neb., p. 203, pi. x, f. 18, 

 (1872); etc. 



Meek's description : " Shell very small, longitudinally sub- 

 ovate, moderately convex, widest posteriorly ; anterior end 

 somewhat narrowly rounded; base forming a semiovate curve, 

 the most prominent part being near the shorter end ; posterior 

 side comparatively wide, and subtruncated ; beaks near the 

 posterior extremity ; hinge line nearly rectangular at the beaks ; 

 denticles comparatively large, about seven on the longer side, 



