Bekdk.] Carboniferous Invertebrate*. 109 



low, rounded sulcus, extending from the back part of the beaks 

 to the middle of the truncated margin behind. Surface marked 

 with fine lines of growth and small irregular, concentric wrin- 

 kles, which latter are not defined on the posterior dorsal region 

 above the umbonal ridge ; crossing these are the usual radiat- 

 ing rows of minute granules. Length, 2 inches ; height, 1.15 

 inches; convexity, 1 inch." 



Range and distribution : Upper Coal Measures ; Kansas 

 City, Iola, Lawrence, Lecompton, Topeka. 



This species may be very easily distinguished from the fore- 

 going by its very much larger size and less angular and more 

 robust form, and the sinuosity of the ventral margin. 



Allorisma subcuneatum. Plate XX, figs. 1-lb. 



Allort.sma reqularis? Owen, Geol. Rep. Wis., Iowa, and Minn., pi. v, f. 



13, (1852). ' 

 Allorisma subcuneata Meek, Fin. Rep. U. S. Geol. Snrv. Neb., p. 221, 



pi. ii, ff. 10a, b, (1872); etc. 



Meek's description : " Shell attaining a large size, longitudi- 

 nally elongated, or twice to three times as long as high, pro- 

 portional length increasing with age ; greatest convexity a little 

 in advance of the middle and in the umbonal region ; cuneate 

 and a little gaping behind, where the margin is more or less 

 narrowly rounded in outline. Basal and dorsal margins nearly 

 parallel, the latter being more or less concave in outline, or 

 nearly straight, and inflected so as to form a lanceolate kind of 

 false area, bounded by an obtuse ridge on each side, just out- 

 side of which there is a shallow undefined sulcus ; basal margin 

 slightly convex, or somewhat straightened along the middle, 

 and sometimes very faintly sinuous just under the beaks, round- 

 ing up more abruptly before than behind ; anterior margin 

 very short, a little gaping and rather prominently rounded be- 

 low ; beaks convex, incurved, and placed near the anterior end, 

 rather depressed, but rising moderately above the dorsal margin. 

 Surface ornamented with fine stria' of growth, and well-defined 

 concentric undulations usually more distinct and regular on the 

 beaks and umbonal region. Length of the largest specimen 

 IS -vi 



