PLATE L1X 



PAGE 



Figs. 1, 2. STROPHEODOXTA VAKISTRIATA Conrad 312 



1. Ventral valve. Striae are nearly equal or alternating in size. 



2. Individual with alternating striae. 



Manlius formation, New York. 



Figs. 3-5. STROPHOXELLA GENICULATA (Hall) 321 



Ventral, dorsal, and side views of a small individual. Helderberg 

 formation, Keyser member, Cumberland. (After Hall.) 



Figs. 6, 7. STROPHOXELLA LEAVEXWORTHANA (Hall) 322 



Dorsal and side views. New Scotland formation, New York. 



Figs. 8-10. STROPHOXELLA PUNCTULIFERA (Hall) 323 



8. Dorsal valve. 



9. Side view of the dorsal valve. 



10. Interior of a more gibbous dorsal valve. 

 New Scotland formation, New York. 



Fig. 11. STROPHOXELLA KEYSERENSIS Swartz n. sp 324 



Interior of dorsal valve. Helderberg formation, Keyser member, 

 Tonoloway. 



Fig. 12. STROPHONELLA HEADLEYANA (Hall) 325 



Exterior of a ventral valve, showing the peculiar interrupted striation. 

 New Scotland formation, New York. 



Figs. 13, 14. STROPHOXELLA UNDAPLICATA Swartz n. sp 326 



13. Dorsal valve. 



14. Small ventral valve. 



Helderberg formation, New Scotland member, Dawson, W. Va. 



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