116 LAMELLIBEA.NCHS. 



parallel to the posterior border ; while on the basal half of the 

 valves they are closely approximate and curve forward. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Forest City ( Holt county ). 



Pinna missouriensis SWALLOW. 



Pinna missouriensis Swallow, 1863: Trans. St. Louis Acad. Sci., vol. II, 

 p. 97. 



A rather large shell with radiating ridges on the posterior 

 slopes. 



Horizon and localities. Lower Carboniferous, Saint Louis 

 limestone : Ste. Genevieve. 



Pinna peracuta SHUMARD. 



Plate xlv, figs. 2a-b. 



Pinna peracuta Shumard, 1858 : Trans. St. Louis Acad. Sci., vol. I, p. 214. 

 Pinna peracuta Meek, 1872: U. S. Geog. and Geol. Sur. Nebraska, p. 198, 



pi. vi, figs, lla-b. 



Pinna peracuta White, 1884: Geol. Sur. Indiana, 13th Ann. Rep., pt. ii, 

 p. 145, pi. xxviii, figs. 1-2. 



Shell attaining a large size, very convex or somewhat 

 cylindrical, flattened behind; hinge-line straight; ventral mar- 

 gin nearly straight ; posterior rounded. Surface smooth, or 

 marked only by lines of growth. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



Lithophaga sp ? 



Plate xlii, figs. 8a-b. 



Shell moderately long, very ventricose, compressed and 

 sharply rounded posteriorly; hinge-line straight, about two- 

 thirds as long as the valves ; beaks obtuse, terminal. Surface 

 marked only by closely arranged lines of growth. 



Horizon and localities. Lower Carboniferous, Burlington 

 limestone : Louisiana. 



