Hkkde.] Carboniferous Invertebrates. 167 



behind the beaks, but very gradually declining, with a slightly 

 convex outline posteriorly ; anterior side quite short, declining 

 very abruptly from the beaks above, and rounded below ; beaks 

 rather depressed, incurved, and located nearer the anterior end 

 than the middle. Surface of cast with moderately distinct, ir- 

 regular concentric undulations, showing behind the beaks dis- 

 tinct impressions of the cartilage fulcra. Length, 1.45 inches ; 

 height, 1.03 inches; convexity, about 0.08 inch." 



Range and distribution : Upper Coal Measures; Cherryvale, 

 Kansas City, Turner, Topeka. 



This species may be distinguished from the foregoing by its 



more undulate and less carinate concentric ridges, which are 



never crenate, and the absence of the nearly obsolete radiating 



stria 1 . 



ALLORISMA. 

 King, Aim. Mas. Nat. Hist.. XIV. p. 315 1 1814 I. 



Allorisma geinitzi. Plate XX, fig. 6. 



Allorisma elegans Geinitz, Garb. u. Dvas in Neb., p. 13, pi. i, f. 31, 



(1866), (non King i. 

 Allorisma I Sedqwickia) geiniizi Meek, Fin. Rep. U. S. Geol. Surv. Neb., 



p. 219, pi. x, ff. 16a, b, (1872). 

 Allorisma geinitzi Meek, Geol. Surv. 111., v, p. 586, pi. xxvi, f. 23, (1873). 



Meek's description : " Shell small, rather compressed, longi- 

 tudinally subovate, abruptly narrowed from the beaks posteri- 

 orly ; umbonal slopes distinctly carinate from the beaks to the 

 posterior basal angle ; anterior side subtruncate, with an ab- 

 rupt slope from the beaks obliquely forward above, and round- 

 ing into the base below ; basal margin somewhat prominently 

 rounded anteriorly, and nearly straight or faintly sinuous be- 

 hind ; posterior end compressed, its margin abruptly truncated 

 vertically, so as to make its upper and lower parts nearly rec- 

 tangular ; cardinal margin sloping, with a slightly concave out- 

 line, from the beaks to the truncated posterior end; beaks 

 elevated, incurved, and placed about half w r ay between the 

 middle and the anterior extremity of the valve. Surface or- 

 namented with numerous minute, closely crowded granules, 

 which, on the umbones and other parts of the valves in front 

 of the angular umbonal slope, show a tendency to arrange 



