PLATE 56. 



Pntrf. 



Fig. 1 - 4 & 8. Platyceras ventricosum. ' 311 



1 a, b. Views of the ujiper and lower side of a young si)ecinien wliidi is a cast. 



2 a. View of a specimen of medium size, looking upon the top of the spire. 



2 4. View of the aperture of the same, showing also tliat the spire is not as higli as tlie outer 



volution. 



"t 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. 



rig. 5, 6, 7 & 9. Platyceras gebuardi. 312 



5 a. View of the s))ire of a specimen of ordinary size. Tlie stria' are not .sufficiently undulated 

 in the drawing. 



o b. Profile of the same from tlie back of the shell. 



I). The spire of another specimen where the last volution is more free near the aperture, and 



slightly carinatod near the apex. 

 7. The cast of a specimen of this species. 

 9. A similar cast, the last volution becoming free. 



