Beede.] Carboniferous Invertebrates. 129 



about half way to the lower end ; beyond the line appears to 

 be a very indistinct furrow near to the ventral margin. In a 

 cast of what appears to be a right valve of another specimen 

 the adductor impression is shown, located nearly opposite to 

 that of the left as described above. It is situated mostly be- 

 hind the umbonal ridge but extends over it, is deeper and 

 roundly ovate. The pallial line extends from the lower side 

 of the impression a little forward and then upward, reaching to 

 the anterior edge of the beak. The umbonal ridge appears to 

 be much less sharp in this specimen than in the other. 



Range and distribution: Upper Coal Measures; Turner, 

 Topeka. 



This species may be easily distinguished from the foregoing 

 by its more slender form, more gently curving front, and less 

 spinous ear. 



Limopteria gibbosa. Plate XVI, fig. 9. 



Pterin* cctftfonopteri a) gibbosa Meek and Worthen, Geol. Surv. 111., ir, 



p. 330, pi. xxvii, ff. 11-llb, (1866). 

 Monapteria gibbosa White, 13th Ann. Rep. Ind. St. Geol., p. 139, pi. xxx, 



ff. 11, 12, (1884). 

 Monnpteria ( Pterim'a) rjibboxn Heilprin, 2d Geol. Surv. Perm., Ann. Rep. 



188-1. p. 455, f. 11a, p. -441, f. 11, (1886). 



White's description : " Shell, exclusive of the wing and pos- 

 terior prominence, irregularly suborbicular in marginal out- 

 line ; the valves moderately convex or a little gibbous ; the 

 anterior and basal margins forming an almost regular semicir- 

 cular curve; posterior portion of the shell produced, narrow r 

 and narrowly rounded, or subangular, at the extremity ; wing 

 slender, compressed and extending backward as far as the nar- 

 row extremity, between which the posterior margin forms a 

 deep, broad notch, that is narrowly rounded at the bottom ; 

 umbonal ridge moderately distinct; beaks equal, not so far 

 forward as the front margin of the shell ; anterior lunule dee]) ; 

 cardinal border not so long as the full diameter of the shell ; 

 surface marked only by the ordinary lines of growth. Length, 

 from posterior extremity to front, 27 mm. ; height, from base 

 to beaks, 23 mm." 



