DEVONIAN FISHES OF IOWA 



125 



Fig. 18. 

 Pig. 18. Rhyyichodus excavatus Newberry. Cedar Valley limestone (Meso-Devonian); 

 Waverly, Iowa. The dental plate here shown is the holotype of Newberry's so-called R. 

 occidentalis. Original in American Museum. Natural size. 



berry unwittingly figured under the name of R. excavatus in 

 his Monograph of 1889. 



That others may judge of the propriety of uniting the two 

 species, we append herewith the original description of R. oc- 

 cidentalis : 



Teeth of small size, much compressed. Anterior margin 

 slightly curved, but nearly vertical. Superior margin gently 

 arched downward from the prominent anterior point, forming 

 a much compressed triturating surface or edge. Posterior por- 

 tion of upper margin acute-edged. Exterior lateral surface stri- 

 ated obliquely backward. Basal margin formed by the edges 

 of external and internal laminae, of which the edges are broken 

 and irregular. From the Hamilton limestone, Waverly, Iowa. 



