PLATE XLI. 



PAGE. 



Fig. 1. WHITELLA RUGATINA, n. sp 569 



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

 apolis, Minnesota. 



Figs. 2 and 3. WHITELLA CONCENTRICA 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 Whitfleld, sp ' 570 



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

 stone, Minneapolis, Minnesota. 



Figs. 6 to 9. WHITELLA COJIPRESSA 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. TRUNCATA 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 PR^CIPTA Ulrich 574 



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

 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. 



572 



Figs. 22 and ? 23. WHITBLLA SUBCARINATA, n. sp 



22. A well preserved internal cast of aright 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 VENTRICOSA Hall, 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 York. 



Figs. 27 and 28. WHITELLA STERLINGENSIS 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 River group, Sterling, 

 Illinois. Illinois State Museum. 



Figs. 29 to 31. SAFFOBDIA MODESTA Dlrich 62; 



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

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

 31. The left side of same x 2. 



Figs. 32 and 33. 



SAFFORDI A SULCODORSATA Ulrich 626 



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

 Hudson River group, near Spring Valley, Minnesota. 



Figs. 34 to 



41. 

 34. 

 35. 



36. 



37. 



38. 



39 and 40. 



41. 



S.UKOHDIA VKNTRALIS, H. Sp 



Cast of the interior of a left valve. Spring Valley, Minnesota. 



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



bryozoan. Hudson River group. Iron Ridge, Wisconsin. 

 Anterior view of same. 

 Hinge of a right valve. 

 A left valve. 

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



626 



original of figure .'17. 



Hinge of the left valve. 



Valley, Minnesota. 



Upper beds of the Hudson River group, near Spring 



