PLATE 55. 



Page 



Fig. 1. Strophostylus eleqans. 304 



1 a. A small specimen which is imbedded in limestone. 

 1 6. A larger individual. 



1 e. A larger specimen, the surface better preserved. 

 1 d. An enlarged figure, showing more distinctly the fine stria; and form of the shell. 



Fig. 2. MURCHISONIA BILIRiTA. 299 



2. A fragment preserving two volutions. 



Fig. 3. Platyostoma? subangulata. 301 



3 o. A lateral view of the specimen. 



3 b. View of the base of the same. 



Fig. 4. Platyostoma depressa. 301 



4 o. 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 i)reserves the impressions of the stria. 



Fig. 5 & 7. Plattceras sinuatum. 314 



6. 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 striie nearer 

 the apex, must have been wider at that period of growth. 



Fig. 6. Platyceras gebiiardi. 312 



6 a. An enlargement of the spire of the specimen fig. 5, Plate lvi; showing the carinatiou 

 along the summit, and the abrupt bending of the stria;. 



6 6. A still farther enlargement, showing the fine revolving strise which cancellate the coarser 

 transverse strisD, and the proportionate size of the two sets. 



Fig. 8. Strophostylus globosus. 305 



8. A cast of this species, preserving a fragment of the shell along the suture. 



Fig. 9. PliATYOSTOMA VENTRIOOSA. 300 



9 a. View of a depressed-globose specimen, from which the shell is nearly removed. 

 9 6. 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, sliowing the undulating strise 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. 



