PELECYPODA—PRIONODESMACEA. 489 



Kentucky, Indiana, Illinois, Kansas, Colorado (Hermosa), Okla- 

 homa (Poteau Group). 

 342. A. pellucidus Meek and Worthen. Carbonic. 



Very small, somewhat oblique, extremely thin and fragile. 

 Ears subequal ; the anterior acutely angular. Surface cancel- 

 lated by the concentric and radiating striae (12 radii in -^ inch at 



Fig. 652. Aviculopecten providencesis. (Kan. Pal., VI /I I.) 



anterior margin). Length and height about equal (|- inch). 

 Hinge line shorter than length of shell below. 

 Illinois, Colorado. 



343. A. providencesis (Cox). (Fig. 652.) Carbonic. 

 Large. Striae in bundles of 3 to 5 which are separated by 



broad grooves. 



Kentucky, Indiana, Missouri, Kansas. 



344. A. interlineatus Meek and Worthen. (Fig. 653.) 



Carbonic. 

 Surface marked only with strong concentric ridges and with 

 fine concentric striae between. 

 Ohio-Missouri, Arizona. 



345. A. curtocardinalis Hall and Whitf. (Fig. 654, a.) 



Carbonic. 

 Smaller than A. occidentalis, with smaller ears and bifurcating 

 simple striae. 



