EXPLANATION OF PLATE XXX. 



Figs. 1-4. Testudo Coksoni : 



Fig. 1. Intermeilinte portion of tbo carapace, one-half the natural size, exhibit-inn; the series 

 of vertebral jilates, from the first to the eighth and part of the ninth, and contiguous por- 

 tions of the costal plates. Specimen cliscovered by Dr. Joseph K. Corson on the buttes of 

 Dry Creek, and jux'sented hy him to the Academy of Philadelphia. 



Fig. 2. Plastron, or lower shield, one-third the natural size. Specimen discovered by Dr. 

 Corson ou Grizzly Buttes, and presented to the Academy. 



Fig. 3. Anterior i)rocess of another plastron, one-half the natural size. From a specimen 

 discovered by Dr. Corson in the same locality as the last. 



Fig. 4. Anterior process of a nearly complete plastron, one-half the natural size. From a 

 specimen discovered by Mrs. Dr. Carter on the buttes of Dry Creek, and presented by her 

 to the Academy of Philadelphia. 



I'ig. 5. CLADOCYCLUS OCCIDENT^iXlS : 



Large scale, imbedded in a lead-colored calcareous shale, natural size. Specimen obtained 

 by Professor Hayden from the Cretaceous formation of Sage Creek, Dakota. 



