PLATE XXXII . 



Olenellus (^Holmia) walcottanus. 



Fig. I. Cast of the under side of the doublure, showing the pits formed bj the 

 semi-spinose inner margin. 



2. A hypostoma attached to the doublure. 



3. An unusually well preserved hypostoma, showing the six spines on each 

 side. 



4. An enlargement (X 2) of posterior segments of the thorax and the 

 pygidium, showing the peculiarities of the surface ornamentation. 



(272) 



