Plate IX. 



EXAMPLES OF STATE QUAERY SYNTHETODONT DEN- 

 TAL PLATES. 



All figures reduced slightly less than the natural size. 



In this plate is shown a representative assortment of the 

 compound dental plates of Synthetodus trisulcatus, with per- 

 haps one or two mutilated examples (Figs. 19, 32) of S. calvini, 

 all from the State Quarry beds near North Liberty, in John- 

 son county, Iowa. The two upper rows represent the normal 

 expression for the type species. 



Originals preserved in the Museum of Iowa State University. 

 Pages 231 and 233 



328 



