PLATE IX. 



Fig. 1. — Plychodus mortoni, end of superior dentition, continuous with left 

 end of fig. 1, plate VIII, but less reduced. 



Fig. 2. — Ptychodus mortoni, a transverse series of teeth, arranged more loosely, 

 from near the right extremity of fig. 1, plate VIII, about two-thirds natural 

 size; the upper series belong one at each end of the lower series. 



