PLATE 30. 
Page 
Figs. 1-9. Spirifera raricosta. . 192 
1. A dorsal view of a young specimen. 
2. A dorsal view of a larger individual preserving a portion of the shell. 
3-6. Dorsal, ventral, profile and front views of a specimen which is very short upon the hinge 
line and of very gibbous form, with less than the usual number of plications. 
7. A ventral valve which is very much extended on the hinge line, presenting much the appear¬ 
ance of S. perlamellosa. 
8. A front view of a specimen, showing the elevation of the fold. 
9. The interior of a ventral valve which is much rounded on the cardinal extremities. 
Figs. 10-15. Spirifera disparilis. 204 
Compare with S. pyxadatus, of the Oriskany sandstone. 
10 -12, 14. Dorsal, ventral, profile and front views of a specimen of ordinary character. 
13. Cardinal view of another individual, showing the area and foramen. 
15. Dorsal view of a larger specimen, showing stronger lateral plications. The figures are all 
enlarged to two diameters. 
Figs.16-20. Spirifera macrothyris. 202 
16. Dorsal view of a large specimen showing the area and foramen of the ventral valve. The shell 
is almost entirely removed, leaving a partial cast on the dorsal side. 
17. A large imperfect ventral valve. 
18. A cardinal view of another specimen, showing the foramen and the striated cardinal area. 
19. Cardinal view of a young individual, showing a more elevated and sharper mesial fold. 
20. A partial cast of the ventral valve, showing the filling of the large muscular imprint. 
Fig. 21. Spirifera unica. 208 
21. An imperfect ventral valve. There is a strong probability that this is identical with S. 
arenosa, of the Oriskany sandstone. 
