PLATE XXV 



PAGE 



Figs. 1-4. OBOLLELA MINOB Walcott 233 



1. Cast of pedicle valve, enlarged. 



2. Exterior of pedicle valve. 



3. Exterior of brachial valve. 



4. Cast of interior of brachial valve and edge view of same. 



Cambrian (Waucoban), near Stissingville, Dutchess County, 

 New York. 



Figs. 5-8. HYOLITHES COMMUNIS Billings 318 



5. 6. Lateral views of two specimens, enlarged. 



7, 8. Transverse sections showing irregularities in thickness of shell. 

 Cambrian (Waucoban), Troy, New York. 



Fig. 9. SCOLITHUS LINEABIS Hiildemaiin 276 



Fragment of drifted Antietam Sandstone, preserving the tubes of 

 this species. 



Pebble, five miles southwest of Washington, D. C. 

 Figures 1 to 8 are after Walcott. 



375 



