Am. Jour. Sci., Vol. V, 1898. 



Plate II. 



The Plastron of Protostega ischyra ( Wieland). 



The under or external view of a series of elements, all of which were found in 

 contact relatively in the above position and beneath all other skeletal parts present. 

 One-twentieth natural size. 



f Rt. H = Right Hyoplastron. 

 ! Rt. Hp. = " Hypoplastron. 

 [ Rt. X. = " Xiphiplastron. 

 [ Ent. = The Entepiplastron (?). 





