PLATE XLI. 



Page. 



Fig. 1. Whitella RUGATINA, n. sp 569 



Left side ol a cast of the interior. Middle third of the Trenton shales, Minne- 

 apolis, Minnesota. 



Figs. 2 and 3. Whitella concentbica Ulrich 569 



The right side and a front view of the type. Middle third of the Trenton shales, 

 Minneapolis, Minnesota. 



Figs. 4 and 5. Whitella megambona Whitfield, sp 570 



Two views, lateral and anterior, of a good cast of the interior. Trenton lime- 

 stone, Minneapolis, Minnesota. 



Figs. 6 to 9. Whitella COMPEBSSA Ulrich 568 



6 and 7. The right side and a front view of an internal cast, differing slightly from the 



type of the species. 

 8 and 9. Two views, side and dorsal, of the original type of the species. Middle third of 



the Trenton shales, Minneapolis, Minnesota. 



Figs. 10 to 14. Whitella TRUNC ATA Ulrich 572 



10 to 12. Dorsal, side and front views of an average specimen. 



13 and 14. The right side and a posterior view of the largest cast of the interior seen. 

 Galena shales, Goodhue county, Minnesota. 



Figs. 15 and 16. Whitella pe^cipta Ulrich 51i 



The left side and a dorsal view of a large and well preserved cast of the inferior. 

 Galena shales, Goodhue county, Minnesota. • 



Figs. 17 to 21 Whitella scofieldi Ulrich 57 1 



17. A very large left valve from the middle third of the Trenton shales at St. Paul, 



Minnesota. 



18. Hinge of same. The cardinal teeth are abnormally developed. 



19 and 20. Anterior and side views of the original type of the species. Middle third, of the 

 Trenton shales, Goodhue county, Minnesota. 

 21. Hinge of same x 2, showing the cardinal teeth, the striated escutcheon and the 

 posterior internal ligament supports in a very satisfactory manner. 



Figs. 22 and ? 23. Whitella subcaeinata, n. sp 572 



22. A well preserved intiernal cast of a right valve. Middle Galena, Wykoff. Minnesota. 



23. Cast of a left valve, supposed to represent an earlier variety of this species. 



Lower Trenton limestone, Jo Daviess county, Illinois. 



Figs. 24 to 26. , Whitella .venteicosa Hal-1, sp 573 



24. Internal cast of a right valve in which the anterior margin is uniformly rounded. 



25. Anterior view of same, with the left valve restored from another specimen. 



26. Outline of the antero-dorsal part of a left valve in which the anterior margin is 



sharply rounded above. Trenton limestone, Watertown, New Yorls. 



Figs. 27 and 28. Whitella steelingensis Meek and Worthen 567 



Antero-cardinal and lateral views of the original type of this species. The speci- 

 men is a cast of the exterior. Upper part of the Hudson Eiver group. Sterling, 

 Illinois. Illinois State Museum. 



Figs. 29 to 31. Saffoedia modesta Ulrich 627 



29 and 30. The left side and a front view of an entire cast of the interior, natural size. 

 The specimen is of the average size. Galena shales, Goodhue county, Minnesota. 

 31. The left side of same x 2. 



Figs. 32 and 33. Saffordia sulcodorsata Ulrich 626 



Antero-cardinal and lateral views of the specimen described. Upper part of the 

 Hudson Elver group, near Spring Valley, Minnesota. 



Figs. 34 to 41. Saffoedia ventealis, n. sp 626 



34. Cast of the Interior of a left valve. Spring Valley, Minnesota. 



35. Gutta-percha impression of a natural mold of a small left valve in the base of a 



bryozoan. Hudson River group, Iron Ridge, Wisconsin. 



36. Anterior view of same. 



37. Hinge of a right valve. 



38. A left valve. 



39 and 40. Anterior and cardinal views of same, with the right valve restored from the 

 original of figure 37. 

 41. Hinge of the left valve. Upper beds pf the Hudson River group, near Spring 

 Valley, Minnesota, 



