LAMELL1BRA.NCHS. 



Entolium circulus (SHUMARD). 



Avicula drculus Shumard, 1855: Geol. Sur. Missouri, Ann. Rep., p. 206, 



pi. C, figs. 14a-b. 

 Avicula circulus Hall. 1858 : Geology Iowa, vol. I, p. 522, pi. vii, fig. 9. 



Large, compressed, circular; hinge very short; surface 

 smooth or marked by fine lines of growth. 



Horizon and localities Lower Carboniferous, Chouteau 

 ( Kinderhook ) limestone : Vandever Falls ( Cooper county ). 



Entolium cooperensis (SHDMARD). 



Avicula cooperensis Shumard, 185"> : Geol. Sur. Missouri, Ann. Rep., p. 206, 

 pi. C, fig. 15. 



A small form somewhat resembling E. circulus, but with 

 shorter hinge-line, and with distinct radiating ribs. 



Horizon and localities. Lower Carboniferous, Chouteau 

 ( Kinderhook ) limestone : Yandever Falls ( Cooper county ). 



Entolium aviculatum (SWALLOW). 

 Plate xlil, figs. 2a-b. 



Pecten aviculatus Swallow, 1858: Trans. St. Louis Acad. Sci., vol. I, p.. 



125. 

 Entolium aviculatum Meek, 1872: U. S. Geol. Sur. Nebraska, p. 189, pi. 



ix, figs, lla-f. 

 Entolium aviculatum White, 1834 : Geol. Sur. Indiana, 13th Ann. Rep., pt. 



ii, p. 142, pi. xxviii, figs. 7-8. 



Shell compressed, very thin, equivalve, subcircular in out- 

 line, with small subequal ears ; anterior and posterior slopes 

 straight, equally inclined to the hinge-line, and forming at the 

 beak an angle of about 120 with each other; hinge-line short. 

 A shallow depression extends from the umbones to the front 

 and back margins of each valve. Surface ornamented by minute 

 concentric lines, which are often crossed by faint radiating 

 striations. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



