PLATE XXX. 
Pauk. 
Figs. 1 to 4. LiNouLASMA oALENKNsis W. and S riVj 
1. Interior ol Lh(! ventral valvt; from a gutta percha improssion. y, umtxinal scar; 
k, mirtcllo; lateral .scars; .s, sc^ptiiin. 
2. Interior of the dorsal valve from a gutta percha irnpre.ssion. rr, crescent; li, 
central .scars; j, anterior scars; t, transverse scars; other letters as in fig. 1. 
3. Profile of the type specimen from vvhich the Impressions of flgs. 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, xo, to show the arrangement of the linear 
series of papillae on the concentric lines of growth. Near the top of the Galena 
limestone, near Ilaniilton, Minn. Minnesota Geological Survey collection. 
Figs. 5 to 7. SCHIZAMBON (?) DODGii, n. sp / 
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 subniarginal beak and the pedicle opening. 
9. The dorsal valve of the same specimen in which^he beak is marginal. 
10. Profile outlineof the same specimen, ^j, pedicle valve. Middle beds of the Hudson 
River group, Cincinnati, Ohio. Collection of C. Schuchert. 
Figs. II to 17. Clitasibonites di versa Shaler, sp 37H 
11 . A dorsal view, showing the elevated area of the ventral valve, in which the dcl- 
tidium has been worn away, exposing the spondylium. (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 V)y a short 
septum (,s). (After Hall.) 
14. Interior of the dorsal valve, cp, cardinal process; adductor scars; o, genital 
markings. Galena shales, near Cannon Falls, Minn. Collection of C. Schuchert. 
15. Interior of another dorsal valve in which thedeltidium 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 adjustor scars on the lateral 
limits of the spondylium, x 2. Galena shales, near Cannon Falls, Minn. Col- 
lection of W. H. Scofield. 
Figs. 18 and 19. Clitambonites diversa, 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; k, foramen or pedicle open- 
ing. (After Hall.) Galena shales, south of Cannon Falls, Minn. Collection 
of C. Schuchert. 
Figs. 20 to 23. ScENiDiUM anthonensis Sardeson 381 
20 and 21. Ventral and cardinal views of a specimen, x 4. Trenton shales, near Cannon 
Falls, Minn. Collection of W. II. Scotield. 
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 (?) scofibldi, 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. Protlle 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 dursal 
valve. Galena shales, near Cannon B'alls, Minn. Minnesota (icdlnLMfiil Survey 
collection. 
Figs. 29 to 31. ANAsTKomiA (?) hemu'licata Hall 382 
29 and :\Q. Dorsal and ventral valves respectively. 
.■}1. Prollle view of the same specimen. Galena shaks near Cannon Falls, Minn. 
Minnesota Geological Survey collection. 
