PLATE 28. 
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1. 481. 1. Cyclonema cancellata. ( Pag. 90.) 
1 a, 6, c, d. Views of several specimens, showing an increasing size and slight variation in form. 
1 e. View of the aperture, the shell being slightly compressed in a vertical direction. 
1 f, g. View of the front of the shell, and aperture of the same. 
1 h. Portion of the surface enlarged, showing the character of the striae. 
2. 482. 2. Cyclonema ventricosa. ( Pag. 90.) 
2 a. Front view of the shell. 2 b. View of the mouth. - 
2 c. A portion of the surface enlarged, showing the character of the striae. 
3 a, b . 483. 3. Cyclonema? obsoleta. ( Pag. 90.) 
4. 485. 1. Platyostoma. ( Pag. 91.) 
4 a. View looking upon the top of the spire. 
4 b. Profile view showing the slight elevation of the spire. 
4 c. Another specimen, view looking upon the spire. 
4 d. View of the aperture, which is angular at the outer margin, probably from pressure. 
5. 484. 4. Cyclonema cancellata? (Pag. 91.) 
5 a. The cast of the shell, which is smooth. 5 b. A portion of the shell from the base, enlarged. 
7. 486. 16. Murchisonia subulata. ( Pag. 91.) 
7 a. A young specimen of this species. 7 b. An elder specimen of the same. 
7 c, d. Two specimens of the largest size observed; the last one wanting one or more of the upper volutions. 
8. 497. 8. Bucania stigmosa. ( Pag. 92.) 
8 a. Dorsal valve of an imperfect specimen. 
8 b. A portion of the same enlarged, showing the elevated decussating striae, and another portion where 
these are obliterated by abrasion or exfoliation. 
8 c. Dorsal view of a cast of this species, with the apeiture and a part of the last volution broken off. 
8 d. Lateral view of the same specimen. 
8 c. Transverse section of the last volution, where broken off. 
9. 488. 9. Bucania? bella-puncta. ( Pag. 93.) 
10. 396. 7. Bucania trilobata. ( Pag. 93.) 
10 a. A specimen, natural size. 
10 b. A large individual, much compressed in a longitudinal direction. 
11. 489. 3. Oncoceras subrectum. (Pag. 94.) 
11 a A lateral view of the fragment. 
11 b. A portion of the surface enlarged, showing a suture on one side. 
12. 494. 1. Cornulites flexuosus. ( Pag. 98.) 
12 a. A specimen, somewhat tortuous in form and partially compressed, covered with the external striated 
shell. 
12 c. A specimen, nearly entire, exhibiting the usual form and surface characters of this fossil. 
12 d. A fragment of a specimen more curved than usual. 
12 c. A longitudinal section of the last, showing the tube filled with fragments of crinoids and shells. 
13. 495. 1. Discosorus conoideus. ( Pag. 99.) 
13 a. One of these bodies of the natural size, preserving eight or nine rings from the apex to the base. 
13 6. The base of one of these discs from another individual. 
13 c. A section of one of these discs exposed by fracture, showing the radiating and fibrous structure of the 
body. 
