PLATE 55. 
Page 
Fig. 1. Strophostylus elegans. 304 
1 a. A small specimen which is imbedded in limestone. 
1 b. A larger individual. 
1 c. A larger specimen, the surface better preserved. 
1 d. An enlarged figure, showing more distinctly the fine striae and form of the shell. 
Fig. 2. Murciiisonia bilirata. 299 
2. A fragment preserving two volutions. 
Fig. 3. Platyostoma? subangulata. sol 
3 a. A lateral view of the specimen. 
3 b. View of the base of the same. 
Fig. 4. Platyostoma dei>ressa. 301 
4 a. A lateral view of a small individual. 
4 b. The lower side of a similar specimen. The umbilicate character is due to the removal of 
the columella; the opening being a cast, which preserves the impressions of the striae. 
Fig. 5 & 7. Peatyceras sinitatum. 314 
5. View looking upon the spire of a small specimen, showing the deep marginal sinuosity and 
the strong wrinkled surface. 
7. A dorsal view of a larger individual which is compressed upon the outer volution, showing 
the narrow linear sinus near the aperture, which, from the bending of the striae nearer 
the apex, must have been wider at that period of growth. 
Fig. G. Platyceras gebiiardi. 312 
6 a. An enlargement of the spire of the specimen fig. 5, Plate lvi; showing the carination 
along the summit, and the abrupt bending of the striae. 
6 b. A still farther enlargement, showing the fine revolving striae which cancellate the coarser 
transverse striae, and the proportionate size of the two sets. 
Fig. 8. Strophosty^lus globosus. 305 
8. A cast of this species, preserving a fragment of the shell along the suture. 
Fig. 9. Platyostoma ventricosa. 300 
9 j. View of a depressed-globose specimen, from which the shell is nearly removed. 
9 b. View of the aperture of the same. [ The figure does not properly represent the specimen.] 
9 c. A globose specimen which preserves a fragment of the shell. 
9 d. A worn specimen, showing a longitudinal section of the shell on one side of the centre. 
Fig. 10 & 11. Platyceras robustum. 313 
10. View of the spire of a large individual, showing the undulating striae and the sinuosities 
of the right side of the aperture. 
11 a. View of the aperture of a smaller specimen, which is a cast. 
11 b. View of the aperture of a similar specimen. 
