PLATE XXXVIII. 



PAGE. 



Figs. 1 to 5. VANUXEMIA DIXONENSIS Meek and Worthen 550 



1 to 3. Lateral, anterior and cardinal views of a large cast of the intsrior. In many 

 specimens the anterior sulcus is deeper than in this one. 



4. View of the interior of a right valve, as shown in a gutta-percha impression. 



5. A small left valve which preserves a portion of the shell. Lower limestone of 



the Trenton formation, Minneapolis, Minnesota. 



Figs. 6 and 7. VANUXEMIA DIXONENSIS, var. INSUETA, n. var 551 



Anterior and lateral views of a perfect cast of the left valve. Trenton limestone, 

 Minneapolis, Minnesota. 



Figs. 8 to 14. VANCXEMIA ROTUNDATA Hall, sp 552 



8. Perfect impression of the inner side of a rather large right valve. Geol. Sur. 



Mus. Eeg. No. 8319. 



9 and 10. Lateral and antero-cardinal views of an entire cast of the interior. 

 11 to 14. Respectively, posterior, anterior, dorsal and side views of the cast of the interior 

 of a right valve of a small variety, differing from the usual form of the species 

 In the more evenly rounded surface of the casts and greater incurving of the 

 beaks. "Lower Blue" beds of the Trenton formation, Janesville, Wisconsin. 



Figs. 15 to 19. VANUXEMIA OBTUSIFRONS Ulrich 554 



15 to 17. Side, anterior and dorsal views of a good cast of the interior. Lower Trenton 

 limestone, Minneapolis, Minnesota. 



18 and 19. The hinge and an external view of a specimen retaining a large part of the shell. 

 Dixon, Illinois. 



Figs. 20 to 22. VANUXEMIA SUBERECTA, n. sp 553 



Three views, dorsal, side and anterior, of a good, though rather small, cast of the 

 Interior. Trenton limestone, Beloit, Wisconsin. Geol. Sur. Mus. Reg. No. 8328. 



Figs. 23 to 26. VANUXEMIA MEDIA, n. sp 553 



23. An internal cast of a right valve. Trenton limestone, Minneapolis, Minnesota. 

 24 to 26. Lateral, anterior and cardinal views of a specimen in which the right side is 

 preserved as an internal cast, while the other retains some of the shell. 

 Trenton limestone, Cannon Falls, Minnesota. 



Fig. 27. VANUXEMIA CRASSA, n. sp 553 



A sharply defined impression of the inner side of a left valve. Middle third of 

 the Trenton shales, Minneapolis, Minnesota. 



Figs. 28 to 31. VANUXEMIA UMBONATA, n. sp 556 



Four views of right valve of this species. 28, anterior; 29, the hinge; 30, cardinal; 

 and 31, lateral. Middle third of the Trenton shales, Minneapolis, Minnesota. 



Fig. 32. VANUXEMIA HAYNIANA Safford, sp :...- 557 



(See also plate XL, and page 470, fig. 36, iv.) 



A cast of the interior of a small right valve. Galena shales, Kenyon, Minnesota. 



Figs. 33 and 34. VANUXEMIA TEUMINALIS Ulrich 556 



33. Anterior views of the two valves shown in fig. 34. 



34. Casts of left and right valves of this species. The former was found in the 



Trenton limestone at Minneapolis, and belongs to the collection of the Geo- 

 logical Survey, in which it bears the Mus. Reg. No. 5100. The latter is from 

 the same horizon at Cannon Falls. 



Fig. 35. VANUXKMIA NIOTA (? Hall) Whitfleld, sp : 560 



The left side of an entire cast of a rather small example. The anterior margin 

 seems to be more oblique than usual for this species. Trenton limestone 

 (V "Upper Buff" beds), Rockton, Illinois. Geol. Sur. Mus. Reg. No. 8325. 



Figs. 36 to 38. VANUXEMIA suBnoTUNDA,n."sp 559 



36. The interior of an imperfect right valve. 



37. External view of a left valve, imperfect in the postero-dorsal region. 



38. Outline cardinal view of the original of fig. 36. Upper part of middle third of 



the Trenton shales.near.Cannon Falls, Minnesota. 



Figs. 39 to 44. VANUXKMIA A iniriTA, n. sp 560 



39 to 41. Anterior, lateral and dorsal views of a nearly perfect cast of a right^valve. This 



specimen is of the average size and proportions. 

 42. Cast of a large left valve that has suffered slightly from pressure, causing slight 



differences in the outline and the anterior side to l' less abrupt than usual. 

 43 and 44. Side and dorsal views of a smaller cast of a right valve in which the anterior end 

 is very obtuse. Middle Galena, Fillmore county, Minnesota. 



Fig. 45. VANUXKMIA SARDESONI Ulrich 555 



(See also plate xxxvu. flgs. 1719.) 



Interior of the left valve as brought out in a gutta-percha impression of the 

 original type of the species. 



