PLATE XLV 



PAGE 



Figs. 1-3. PIANODEMA suBEQUATA (Conrad) 249 



Pedicle and brachial valves of a well preserved example and profile of 

 the same. 



Ordovician (Mohawkian), Black River (Decorah) shales, 

 Minneapolis, Minnesota. 



Fig. 4. RAFINESQUINA MINNESOTENSIS (Winchell) 261 



Brachial valve of the type form of this species. 



Ordovician (Mohawkian), Black River Is., Rocktown, Wis- 

 consin. 



Figs. 5, 6. RAFINESQUINA MINNESOTENSIS INQUASSA (Sardeson) 264 



Dorsal and profile views of an ordinary example of this variety. 

 Ordovician (Mohawkian), Black River (Platteville) Is., Mineral Point, 

 Wisconsin. 



Fig. 7. RECEPTACULITES OCCIDENTALIS Salter 194 



Weathered surface of an imperfect specimen. 



Ordovician (Mohawkian), Black River portion of Jackson- 

 burg Is., near Springdale, New Jersey. 



Figs. 8, 9. DINOBTHIS PECTINELLA (Emmons) 248 



8. Pedicle valve. 



9. Incomplete brachial valve. 



Ordovician (Mohawkian), Lowest Trenton portion of Jackson- 

 burg Is., near Newton, New Jersey. 



Figs. 10-12. HEBEBTELLA BELLAKUGOSA (Conrad) 239 



10. Exterior of a large pedicle valve. 



11. Interior of the same. 



12. Exterior of a dorsal valve of the ordinary size. 



Ordovician (Mohawkian), Trenton shales of Minnesota. 



Figs. 13, 14. AMPYX ( LONCHODOM AS ) NORMALIS (Billings) 336 



Head and pygidium. 



Ordovician, Chazyan of Newfoundland. 



Figs. 15-20. ECHINOSPHERITES AURANTIUM var AMERICANUM Bassler n. var. 207 



15. A specimen of average size showing the ovate form of this variety. 



16. A well preserved small example preserving the point of attach- 



ment at the base. X 2. 



17. A slightly distorted but otherwise typical specimen. 



18. Compressed example with plates exposed by weathering. 



19. Abraded outer surface of the plates showing pore rhombs. X 3. 



20. Inner surface of calyx plates exhibiting pores. X 3. 



Ordovician (Mohawkian), Echinospherites bed of Chambers- 

 burg Is., 3% miles north of Greencastle, Pennsylvania. 



Figs. 1-3, 5, 6, 10-12 are after Winchell and Schuchert; 7-9 

 after Weller; and 13, 14 after Billings. 



395 



