562 NORTH AMERICAN INDEX FOSSILS. 



CLX. Cyprimeria Conrad. 

 Similar to Venus but right valve with two cardinal teeth, the 

 posterior bifid ; left valve with three cardinals ; each valve with a 

 posterior lateral. Pallial sinus very shallow. Resilium usually 

 external, embraced by the ligament. Comanchic-Cretacic. 



555. C. texana (Roemer). (Arcopagia texana.) Comanchic. 

 Nearly circular, very thin, owing to slight convexity of valves ; 



valves slightly unequal with a somewhat twisted appearance. 

 Very abundant in the Fredericksburg of Texas. 



556. C. crassa Meek. Comanchic-Cretacic. 

 Differs from C. texana in its larger size and much greater thick- 

 ness. Height, 67 mm.; length, 78 mm.; depth, 23 mm. 



Fredericksburg and Eagle Ford of Texas. Fredericksburg and 

 Washita of northern Mexico. 



557. C. excavata (Morton). Cretacic. 

 Posterior portion of shell obliquely truncate. 



Ripleyan of New Jersey (Marshalltown-Navesink), Gulf region. 



CLXI. Clementia Gray. 

 Thin-shelled, inflated. Beaks prominent. Valve margins entire. 

 Surface concentrically sculptured. Anterior left and two posterior 

 right hinge teeth more or less bifid ; no lateral teeth present. Pal- 

 lial sinus long and angular, narrow and ascending. Tertiary-Re- 

 cent. 



558. C. inoceriformis (Wagner). (Fig. 771.) Miocenic. 

 Posterior hinge area marked by an angular ridge, which is wedge- 



Fig. 771. Clementia inoceriformis, left and right valves, X %- ( Md - Surv.) 



