61 



a straight ridge extends from one outer angle of the plates to 

 the other, so as to form a hinge on which the second radials 

 articulate. 



Azygous plates small, quadrangular and inserted between a 

 subradial and the under sloping side of the first radial, on the 

 right, and abutting another subradial. It is followed by 

 another plate, as indicated by the notch between it and the top 

 of the first radial on the left. 



Found in the Upper Coal Measures, at Kansas City, Missouri, 

 and now in the collection of Wm, F. E. Gurley. 



