PLATE 21 



Syringothyris occidentalis (Swallow) 

 Page 103. 



Figs. 1, 2, 3. Cardinal area, brachial, and pedicle views of well-preserved moulds of 

 interiors. (Collection of D. K. Greger. Photos by D. K. Greger.) 



Spirifer varicosus Hall 

 Page 102. 



Figs. 4 and 5. Small pedicle valves. (X2). 

 (Mineola of Ralls County.) 



A try pa reticularis (Linnaeus) 

 Page 97. 



Fig. 6. A specimen with well-preserved spines. (X2/3.) 



(Callaway limestone of Callaway County.) 

 Fig. 7. Brachial view of a large old specimen. (X2/3.) 



(Snyder Creek shale of Callaway County.) 



Proetus crassimarginatus Hall and Clark 

 Page 125. 



Fig. 8. Front of a fragmentary cephalon. (X2). 



Fig. 9. A small pygidium (X2). 



Fig. 10. Front of a cephalon of average size. 



(Mineola of Montgomery County.) 



Dipterus mordax Eastman 

 Page 128. 



Fig. 11. The only specimen known from the Callaway limestone. (X4). 



Ptyctodus ferox Eastman 

 Page 127. 



Fig. 12. Top of the best specimen collected from the Missouri Devonian. 

 (Snyder Creek shale of Callaway County.) 



