114 LAMELL1BRANCHS. 



Monopteria gibbosa (MEEK & WORTHEN), 

 t Plate xliii, figs. 2a-b. 



Pterinea (Monopteria) gibbosa Meek & Worthen, 1866 : Trans. Chicago Acad. 



Sci., vol. I, p. 20. 

 Monopteria gibbosa Meek & Worthen, 1866: Geol. Sur. Illinois, vol. II, 



p. 340, pi. xxvii, figs, ll-llb. 



Monopteria gibbosa White, 1884 : Geol. Sur. Indiana, 13th Ann. Kept., pi. ii, 

 p. 139, pi. xxx, figs. 11-12. 



Shell suborbicular in outline, gibbous, regularly curved 

 along the anterior and basal margins ; posterior margin pro- 

 duced backward, the umbonal ridge extending from the beak 

 to this rounded angularity. Hinge-line straight, somewhat 

 shorter than greatest length of valves, the posterior alate pro- 

 jection rather long, slender, compressed, with a deep sinus be- 

 low, separating it from the valves beneath. Anterior ear very 

 small. Surface marked only by fine concentric lines of growth. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



Monopteria longispina (Cox). 



Plate xlili, fig. 1. 



Oervillia longispina Cox, 1857: Geol. Sur. Kentucky, vol. III. p. 568, pi. 



viii, fig. 6. 



Gervillia auricula Stevens, 1858 : Am. Jour. Sci., (2), vol XXV, p. 265 , p. 38. 

 Pterinea (Monopteria) longispina Meek & Worthen, 1866 : Geol. Sur. Illinois, 



vol.11, p. 341. 



Like M. gibbosa, but very much more oblique, the posterior 

 angle much more produced, the beaks placed more forward. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures: Kansas City. 



Monotis? gregaria MEEK & WORTHEN. 



Monotis ? gregaria Meek & Worthen, 1870: Proc. Acad. Nat. Sci., Phila. 

 Monotis ? gregaria Meek & Worthen, 1875 : Geol. Sur. Illinois, vol. V, p. 573. 

 pi. xxvi, figs. 5a-h. 



A very small, thin, rounded shell, like Aviculopecten, 

 but without the ears defined. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures: Kansas City. 



