EXPLANATION OF PLATE III. 



Figs. 1-3. Merycochcerus rusticus. Figures of the natural size. Specimens from Sweetwater River, 

 Wyoming. Hayden's collection of 1870. 



Fig. 1. Upper jaw, with a nearly complete series of teeth, the last molar introduced from 

 another specimen. 



Fig. 2. Front view of the same specimen, exhibiting the high alveolar border and the nar- 

 row nasal orifice. 



Fig. 3. Lower jaw, with a full series of molar teeth. 



Fig. 4-6. Testudo or Stylemys niobbarensis. Figures of the natural size, except Figure 6, which is 

 one-half the size of nature. From the Niobrara River. Hayden's collection of 1857. 



Fig. 4. Internal view of the fore-part of the plastron. 



Fig. 5. The last vertebral and the pygal plates. 



Fig. 6. Internal view of a posterior portion of the carapace, exhibiting the costal capitula, 

 and the processes for conjunction with the pelvic girdle. 



