PELECYPODA—PRIONODESMACEA. 509 



Very abundant in Washita of Texas. 



CIV. Lima Bruguiere. 

 Shell inflated, marked with radial sculpture. Valves equal, 

 gaping anteriorly and sometimes posteriorly. Beaks pointed. 

 Hinge line straight, terminating in slightly unequal ears. Hinge 

 area of each valve triangular and with central resiliifer. Teeth 

 absent. Muscle impression single and large. Carbonic-Recent. 



398. L. retifera Shumard. (Fig. 681.) Carbonic. 

 Surface marked with about 25 angular ribs about equalling the 



spaces between, becoming obsolete on the umbo. Entire shell 

 covered with numerous, fine concentric striae. 

 Coal Measures : Ohio-Oklahoma. 



399. L. wacoensis Roemer. Comanchic. 

 Differs from L. utahensis in being slightly larger, more oblique 



(obliquity about 45 °), and more ventricose. Radiating ribs 



Fig. 681. Lima retifera. (Kan. Pal., VI/II.) 



Fig. 682. Lima utahensis, internal left mold of valve. (After Stanton.) 



coarser, more angular, less uniform in size, and less regularly 

 arranged. The ribs frequently increase by implantation and 

 bifurcation. 



Washita : Texas, Mexico ; also Fredericksburg of Mexico. 

 400. L. utahensis Stanton. (Fig. 682.) Cretacic. 



Moderately convex. Small. 



Coloradoan : Utah, Mexico. 



CV. Anomia Linne. 

 Thin, translucent, irregular or subcircular, attached by a calci- 

 fied byssus passing through a rounded sinus near the umbo of the 

 right valve. Right valve flattened, conforming to subjacent sur- 

 face, bearing a central adductor impression. Left valve larger, 

 convex, with four muscle scars on a central area, — three byssal 

 and one adductor. Teeth absent. Ligament more or less internal 

 and supplemented by a resilium. Jurassic-Recent. 



