PLATE XXXIX. 



PAGE. 



Figs. 1 to 5. VANUXEMIA DECIPIENS, n. sp 562 



1 to 3. Lateral, dorsal and anterior views of the largest cast of the interior seen. 

 4 and 5. Side and dorsal views of a smaller cast of a right valve. Qeol. Sur. Mus., Reg. 

 No. 8626. 



Figs. 6 and 7. VANUXEMIA WOBTHENI Ulrich 561 



The left side and an anterior view of a nearly perfect cast of the interior. Upper 

 Galena, Jo Daviess county, Illinois. 



Figs. 8 to 12. CYRTODONTA OBESA, n. sp 542 



8 to 10. Three views of a typical shell of this species. Black Elver limestone, Mercer 



county, Kentucky. 



11 and 12. A small specimen of the natural size and x 2, referred to this species with some 

 doubt. Middle third of the Trenton shales, St. Paul, Minnesota. 



Ji*. FIgS. 13 to 15. OllLUOEOH'l'A GIBBERA, n. 8p 542 



Three views of the specimen described. It is a cast of the interior. Base of the 

 middle Galena, Goodhue county, Minnesota. Mus. Geol. Sur. Eeg. No. 8366. 



Figs. 16 to 19. CYBTODONTA ROTULATA, n. sp 541 



16 and 17. Side and profile views of a large internal cast, from the middle third of the 



Trenton shales near Fountain, Minnesota. Geol. Sur. Mus. Reg. No. 8336. 

 18 and 19. Two views of the testiferous type of the species. Black River limestone, Mercer 

 county, Kentucky. 



Figs. 20 to 23. CYBTODONTA AFFINIS, n. sp 540 



20 to 22. Side and dorsal views, and the hinge of a right valve. Middle third of the 



Trenton shales, Goodhue county, Minnesota. 



23. A cast of the interior of the var. flllmorenais. Middle Galena, Fillmore county, 

 Minnesota. 



Figs. 24 and 25. CYBTODONTA PABVA, n. sp 541 



The left side of an entire cast of the interior of the natural size and x 2.3. 

 Middle Galena near Fountain, Minnesota. 



Figs. 26 and 27. CYRTODONTA JANESVILLENSIS, n. sp 637 



Casts of a small right and a larger left valve. The central part of the surface in 

 the latter is broken in the specimen, but has been restored in the drawing. 

 "Lower Blue" beds of the Trenton, Janesville, Wisconsin. Geol. Sur. Mus. 

 Reg. No. 8323. 



Figs. 28 to 33 and ?45. CYBTODONTA BUDOVATA. m op i 536 



28, 31 and 32. Three views of an entire and well preserved-shell. Birdseye limestone. 



High Bridge, Kentucky. 



29. An old left valve from the Black River limestone, or the base of the 



Trenton of Mercer county, Kentucky. 



30. Right side of a cast of the interior from the middle third of the Trenton 



shales, St. Paul, Minnesota. 



33. The hinge of a right valve from High Bridge, Kentucky. 



45. A cast of the interior of a right valve which is doubtfully referred to this 

 species. The bight of the specimen has evidently been reduced by 

 pressure. Trenton limestone, Cannon Falls, Minnesota. 



Fig. 34. CYRTODONTA AHPLA, n. sp 538 



An Imperfect cast of the interior of a large left valve. Trenton limestone, 

 Cannon Falls, Minnesota. 



Figs. 35 and 36. CYBTODONTA OBLIQUA Meek and Worthen 540 



The left side and a front view of the original type of this species. Illinois State 

 Museum. Galena limestone, Scales Mound, Illinois. 



Figs. 37 to 40. CYRTODONTA GLABELLA Ulrich 543 



37 and 38. Two views of the original type of the species. Middle third of the Trenton 



shales, Minneapolis, Minnesota. 



39 and 40. Two sharply defined internal casts of opposite valves, showing slight variations 

 In the outline. Trenton limestone, Beloit, Wisconsin. 



Figs. 41 to 44. CYRTODONTA PEBSiMiLis, n. sp 544 



41 to 43. Three views of an excellent cast of the interior. "Lower Blue" beds of the 



Trenton formation, Beloit, Wisconsin. 

 44. A small right valve from the limestone at Minneapolis, Minnesota. 



Fig. 46. CYBTODONTA OVIKOBMIS Ulrich 544 



(See also plate XL. fig. 1.) 



Mold of the Interior of a left valve, with a. portion of the shell remaining. 

 "Lower Blue" beds of the Trenton formation, Janusvilli*, Wisconsin. 



