EXPLANATION OF PLATE XIII. 



BaSna akenosa : 



Figures one-half the natural size. 



Figs. 1, 2. Specimen on which the genus and species were originally estahlished. Dis- 

 covered at the junction of the Big Sandy and Greeu Rivers, Wyomiug, during Profe.ssor 

 Hayden's exploration of 1870. 



Fig. 1. View of the carapace. 



Fig. 2. View of the plastron, its anterior extremity lost. 



Fig. 3. View of the plastrou of another specimen, originally referred to a species with the 

 name of Baina affinis. It was discovered by Dr. Carter at Chnrch Buttes, and was pre- 

 sented by him to the Academy of Natural Sciences of Philadeljihia. 



