PLATE 56. 
Page 
1 - 4 & 8. Platyceras ventricosum. 311 
1 ft, b. Views of the upper and lower side of a young specimen which is a cast. 
2 a. View of a specimen of medium size, looking upon the top of the spire. 
2 b. View of the aperture of the same, showing also that the spire is not as high as the outer 
volution. 
3 a. View of the spire of a larger specimen : the last volutions are obscured. The surface 
preserves a few obscure wrinkles. 
3 b. Aperture of the same. 
4. The specimen is a partial cast, preserving a small portion of the shell, and showing very 
distinctly the volutions of the spire. 
8. A cast of the same species. 
5, 6, 7 & 9. Platyceras gebhardi. 312 
5 a. View of the spire of a specimen of ordinary size. The striae are not sufficiently undulated 
in the drawing. 
5 b. Profile of the same from the hack of the shell. 
6. The spire of another specimen where the last volution is more free near the aperture, and 
slightly carinated near the apex. 
7. The cast of a specimen of this species. 
9. A similar cast, the last volution becoming free. 
