556 



NORTH AMERICAN INDEX FOSSILS. 



534. L. subundata Hall and Meek. Cretacic. 

 Similar to L. cretacea in form but is usually smaller, rarely reach- 

 ing .5 inch in height, and with finer and closer concentric lines. 



Coloradoan : Utah. Pierre : South Dakota, Montana, Assiniboia. 

 Fox Hills of Wyoming. 



535. L. cretacea Whitfield. Cretacic. 

 Hinge line nearly straight. Surface marked with a deep con- 

 striction passing from the beak to the posterior margin. Concen- 

 tric lines distant and lamellose. 



New Jersey (Cliffwood-Red Bank). 



536. L. occidentalis Morton. (Fig. 



761.) Cretacic. 



Broadly oval, rounded anteriorly, 

 somewhat truncated posteriorly. Poste- 

 rior flattening of shell nearly obsolete. 

 Hinge line nearly straight, slightly de- 

 clining posteriorly. Surface crossed by 

 Lucina occidenta- distinct concentric lines. Large speci- 

 mens measure — height 1.5 inches ; 



Fig. 761. 



is, left valve. 



(After Gilbert.) 



length slightly more. 



Pierre : Colorado and Kansas-Canada. 

 Dakota. 



537. L. aquiana Clark. (Fig. 762, c, d.) 



Fox Hills of South 



Eocenic. 



FlG. 762. a, b, Lucina curta (L. uhleri Clark), left valve ; c, d, L. aquiana, right 

 valve ; e, L. smithi (L. whitei Clark), left valve. All enlarged. (Md. Surv.) 



