124 University Geological Survey of Kansas. 



thern ; the beak, too, is higher and more pointed, as well as 

 having a more tumid umbo." 



Range and distribution : Upper Coal Measures ; Lawrence. 



Aviculopecten coxanus. Plate XIX, fig. 2. 



Aviculopecfe?i coxanus Meek and Worthen, Proo. Acad. Nat. Sci. Phil., 

 p. 453, (1860) ; Meek, U. S. Geol. Surv. Neb., p. 196, pi. ix, ff. 6a,b, (1872). 



Meek's description: "Shell very small; thin, compressed, 

 slightly oblique ; broad subovate exclusive of the ears ; basal 

 margin rounded ; anterior margin more or less rounded, rather 

 straight and oblique above ; posterior margin more prominent 

 than the anterior, often subangular at the point where the pos- 

 tero-basal margin rounds up to meet the obliquely sloping edge 

 above. Hinge generally a little less than the greatest breadth 

 of the valves below. Left valve with anterior ear of moderate 

 size, flat, triangular, with the extremity generally a little less 

 than a right angle, sometimes very slightly rounded, separated 

 from the margin below by an abruptly rounded or subangular 

 sinus ; posterior ear slightly larger and much more acutely 

 angular than the other, but shorter than the most prominent 

 part of the margin below, from which it is separated by a mod- 

 erately deep rather broadly rounded sinus ; beak small, com- 

 pressed, scarcely projecting beyond the cardinal margin, and 

 placed a little in advance of the middle of the hinge ; surface 

 ornamented with linear, simple, often more or less flexuous 

 costse, which alternate in size, the smaller ones dying out at 

 varying distances between the free margins and the umbo — 

 crossing all of these are numerous, extremely fine, regular, 

 closely arranged concentric strise, which, like the costse, are 

 more or less distinctly defined on the ears, as well as on the 

 body of the valve. Right valve unknown." 



Range and distribution: Upper Coal Measures; Lecompton. 



A single specimen of a left valve of this species agreeing very 

 well indeed with Meek's description and figure was collected in 

 the shale underlying the Upper Oread limestone at Lecompton. 



