5io 



NORTH AMERICAN INDEX FOSSILS. 



Fig. 683. Anomia propatoris, 

 upper valve slightly enlarged. 

 (After Stanton ) 



401. A. argentaria Morton. Cretacic. 

 Upper valve with submarginal apex ; its surface covered with 



irregular growth lines and at times with faint radiating striae. 



Ripleyan of New Jersey (Clififwood-Red Bank), Atlantic and 

 Gulf regions to Mexico. 



402. A. propatoris White. (Fig. 683.) Cretacic. 



Shell a little obliquely subovate. Beak 

 of upper valve depressed. Surface mark- 

 ed with rather coarse growth wrinkles 

 and a few radiating ones and by fine, 

 raised radiating striae. Differs from A. 

 gryphorhynchus in having a less promi- 

 nent and rounded umbo, in possessing 

 radial and concentric wrinkles and radial 

 striae. 

 Coloradoan : Colorado, Utah, New Mexico. Montanan : Utah. 



403. A. gryphorhynchus Meek. Cretacic. 

 Elongate, convex. Beak elevated. Growth lines not strong. 



Brackish water. 



Montanan : Montana, Wyoming, Assiniboia, Mexico ? Laramie : 

 Colorado, Wyoming. 



CVI. Placunopsis Morris and Lycett. 



Free or attached, without foramen for passage of byssus. 

 Rounded, thin, with upper or right valve irregularly convex, 

 and lower or left valve flat or, when sessile, 

 conforming to the surface to which it was attach- 

 ed. Beaks very small, central. Surface marked 

 with irregular radiating lines and broad, faint 

 concentric wrinkles. Carbonic-Cretacic. 



404. P. carbonaria Meek and Worthen. )Fig. 



684.) Carbonic. 



Concentric and radiating lines nearly obliter- 

 ated by an oblique series of ridges. 



Ohio-Kansas. 



CVII. Paranomia Conrad. 



Irregular, inequivalve. Upper valve depressed-convex. Lower 

 valve flattened, often attached near the umbo to other objects, 



Fig. 684. Placu- 

 nopsis carbonaria. 

 (Kan. Pal., VI/II.) 



