

PLATE XXX. 



PAGE. 

 Figs. 1 to 4. LINGULASMA GALENENSIS W. and S 354 



1 . Interior of the ventral valve from a gutta percha impression, g, umbonal scar; 



k, middle; I, lateral scars; s, septum. 



2. Interior of the dorsal valve from a gutta percha impression, er, crescent; h, 



central scars; j, anterior scars: t, transverse scars; other letters as in flg. 1. 



3. Profile of the type specimen from which the impressions of figs. 1 and 2 were 



made. The space between the dotted line and the natural cast shows the 

 relative thickness of the shell. 



4. A portion of the exterior surface, x 5, to show the arrangement of the linear 



series of papillae on the concentric lines of growth. Near the top of the Galena 

 limestone, near Hamilton, Minn. Minnesota Geological Survey collection. 



Figs. 5 to 7. SCHIZAMBON (?) DODGII, n. sp 361 



5. View of the ventral valve, showing the strongly lamellose concentric lines, spine 



bases and pedicle opening, x 2. 



6. A dorsal valve preserving some of the surface spines, x 2. 



7. Profile outline to show the relative convexity of valves and the projecting 



beak of the ventral valve, x 2. Upper Trenton at Sandy Hill, New York. Col- 

 lection of C. Schuchert. 



Figs. 8 to 10. SCHIZAMBON (?) LOCKII, n. sp 362 



8. The ventral valve, showing the submarginal beak and the pedicle opening. 



9. The dorsal valve of the same specimen in which the beak is marginal. 



10. Profile outline of the same specimen, p, pedicle valve. Middle beds of the Hudson 



River group, Cincinnati, Ohio. Collection of C. Schuchert. 



Figs. 11 to 17. CLITASIBONITES DIVERSA Shaler, sp 378 



11 . A dorsal view, showing the elevated area of the ventral valve, in which the del- 



tidium has been worn away, exposing the spbndylium. (After Hall.) 



12. Ventral view of the same specimen. The distorted beak is not accidental, but a 



feature often developed in the species. (After Hall.) 



13. Interior of the ventral valve, showing the spondylium (sp) supported by a short 



septum (s). (After Hall.) 



14. Interior of the dorsal valve, cp, cardinal process; ad, adductor scars; o, genital 



markings. Galena shales, near Cannon Falls, Minn. Collection of C. Schuchert. 



15. Interior of another dorsal valve in which the deltidium is preserved. The impres- 



sions of the vascular system are also shown on each side of the septum, and 

 posterior to these are the genital markings. 



16. A portion of flg. 15 in which the deltidium is broken away to show the muscular 



scars of the spondylium, x 2. 



17. An oblique view of the same specimen, to show the adjuster scars on the lateral 



limits of the spondylium, x 2. Galena shales, near Cannon Falls, Minn. Col- 

 lection of W. H. Scofleld. 



Figs. 18 and 19. CLITAMBONITES DIVEKSA, var. ALTISSIMA, n. var 381 



18. Profile view, to show the great elevation of the ventral valve. 



19. Cardinal view of the same specimen. D, deltidium; r, foramen or pedicle open- 



ing. (After Hall.) Galena shales, south of Cannon Falls, Minn. Collection 

 of C. Schuchert. 



Figs. 20 to 23. SCENIDITTM ANTHONENSIS Sardeson 381 



20 and 21. Ventral and cardinal views of a specimen, x 4. Trenton shales, near Cannon 



Falls, Minn. Collection of W. H. Scofleld. 



22 and 23. Views of the exterior and interior of a dorsal valve. (After Hall.) Glade lime- 

 stone, Lebanon Tennessee. 



Figs. 24 to 28. ANASTROPHIA (?) SCOFIELDI, n. sp 383 



24 and 25. Views of the dorsal and ventral valves respectively. 



26. Profile view of the same specimen. 



27. Cardinal view of a distorted specimen, showing an area on the dorsal valve, x 3. 



28. Profile outline, through the center of the shell, to show the extent of the spon- 



dylium, and the septum in the ventral valve, and the septal plates of the dorsal 

 valve. Galena shales, near Cannon Falls, Minn. Minnesota Geological Survey 

 collection. 



Figs. 29 to 31. ANASTKOPHIA (?) HEMIPLICATA Hall .- 382 



29 and 30. Dorsal and ventral valves respectively. 



31. Profile view of the same specimen. Galena shales near Cannon Falls, Minn. 

 Minnesota Geological Survey collection. 



