110 LAMELLIBBANCHS. 



Aviculopecten magna (SWALLOW). 



Plate xliii, tig. 7. 

 Avicula magna Swallow, 1863 : Trans. St. Louis Acad. Sci., vol. II, p. 98. 



Shell very large, heavy, subcircular in outline; anterior 

 and ventral margins regularly rounded ; hinge -line straight, 

 long, nearly equaling the length of the valves. Left valve 

 quite convex, especially toward the umbo ; beak gibbous, ex- 

 tending slightly beyond the hinge-line; posterior ear short; 

 anterior ear greatly extended. Surface marked by rather large, 

 rounded costse radiating from the beak, .and widely separated 

 from one another; these are crossed by lines of growth, often 

 somewhat imbricated. 



Horizon and localities. Lower Carboniferous, Burlington 

 limestone : Springfield (Greene county). 



Aviculopecten missouriensis (SHUMARD). 



Pecten missouriensis Shumard, 1855: Geol. Sur. Missouri, Ann. Rep., p. 

 207, pi. C, fig. 16. 



A small form similar to A. occidentalism but having rela- 

 tively larger ribs. 



Horizon and localities. Lower Carboniferous, Saint Louis 

 limestone : Saint Louis. 



Aviculopecten occidentalis (SHUMARD). 



Plate xlii, fig. 3. 

 Pecten occidentalis Sbumard, 1855: Geol. Sur. Missouri, Ann. Rep., p. 



207, pi. C, fig. 18. 

 Pecten cleavelandicus Swallow, 1858: Trans. St. Louis Acad. Sci., vol. 1, 



p. 184. 

 Aviculopecten occidentalis ? Meek & Worthen, 1866 : Geol. Sur. Illinois, vol. 



II, p. 331, pi. xxvii, figs. 4, 5. 

 Pecten misscuriensis ? Geinitz, 1866 : Garb und Dyas in Nebraska, p. 35, 



tab. ii, fig. 18. (Not Shumard, 1855.) 

 Aviculopecten occidentalis Meek, 1872: U. S. Geol. Sur. Nebraska, p. 191, 



pi. ix,fig. 10. 

 Aviculopecten occidentalis White, 1884: Geol. Sur. Indiana, 13th Ann. Rep., 



pt. ii, p. 143, pi. xxviii, fig. 3. 



Shell of medium size, inequivalye, symmetrical, higher than 

 long, regularly rounded below ; hinge-line as long as> the great- 

 est length of valves. Left valve decidedly convex; other one 



