CHAPTER XII. 



LAMELLTBRANCHS. 



Placunopsis carbonaria MEEK & WORTHEN. 



Plate xliii, fig. 9. 

 Placunopsis carbonaria Meek & Worthen, 1866: Proc. Chicago Acad. Sci., 



vol. I, p. 13. 



Placunopsis carbonaria Meek & Worthen, 1873: G-eol. Sur. Illinois, vol. V, 

 p. 578, pi. xvii, figs. 2a-b. 



Lenticular, compressed, shell very thin. 

 Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures: Kansas City. 



Lima retifera SHUMARD. 

 Plate xlii, fig. 1. 



Lima retifera Shumard, 1858 : Trang. St. Louis Acad. Sci., vol. I, p. 214. 

 Lima retif 'era Geinitz, 1866: Garb, und Dyas in Nebraska, p. 36, tab. ii, 



figs. 20, 21. 



Lima relifera Meek, 1872: U. S. Geol. Sur. Nebraska, p. 188, pi. ix, fig. 5. 

 Lima retifera White, 1884 : Geol. Sur. Indiana, 13th Ann. Kept , pt. ii, p. 



138, pi. xxviii, fig. 4. 



Crenipecten retif erus Miller, 1890: N. A. Geol. and Pal., p. 473. 

 Lima retifera Keyes, 1891: Proc. Acad. Nat. Sci., Phila., p. 248. 



Shell rather small, subovate, moderately convex, regularly 

 rounded below ; anterior slope long, straight, forming an angle 

 of about 140 with the hinge-line, sharply curved as it meets 

 the ventral margin ; posterior slope much shorter ; hinge-line 

 about one-third the length of the valves ; ears subequal ; um- 

 bones not prominent, and situated midway between the extremi- 

 ties of the hinge-line. Surface marked by from 20 to 25 rather 

 angular radiating ribs, which are often crossed by transverse 

 lines of growth. 



Horizon and localities- Upper Carboniferous, Coal Meas- 

 ures: Clinton (Henry county), Kansas City. 



