DEVONIAN FISHES OF IOWA 105 



This species, together with the one immediately to be de- 

 scribed, is known by a number of examples of striated teeth from 

 a peculiar deposit of the Upper Devonian in the vicinity of Elm- 

 hurst, Illinois. As described by Dr. Stuart Weller, who first 

 noted the discordant relations of these beds, their contained 

 fossils are deeply buried in fissures of Niagara limestone, ap- 

 pearances indicating that the joints were open, and became filled 

 with sand and organic remains during the late Devonian. The 

 same sort of unconformity has also been observed and described 

 by Dr. J. M. Clarke at Buffalo, New York, between the upper- 

 most Silurian and Oriskany sandstone. 



Formation and locality. Upper Devonian; Elmhurst, Illinois. 



Diplodus striatus Eastman. 



(Plate I, Figs. 1, 16) 



1899. Diplodus striatus C. R. Eastman, Journ. Geol. 7, p. 490, pi. 7, figs. 3, 4. 

 1899. Diplodus striatus S. Weller, Journ. Geol. 7, p. 484. 



1907. Diplodus striatus C. R. Eastman, Mem. N. Y. State Mus. 10, p. 60, 

 pi. 1, figs. 10, 11. 



Of this species only a few fragmentary teeth were obtained by 

 Dr. Weller from the same locality as the last, the largest and 

 most perfect being represented in Plate I, figure 1. It attains 

 apparently about twice the size of the preceding form, and is dis- 

 tinguished from it by its finer striation, shallower root, and some- 

 what compressed section of its principal cones. The striae on 

 the anterior face all curve uniformly in a spiral direction, but on 

 the posterior face their tendency is to curve outward on either 

 side of the median line to the lateral margin of the cones, where 

 they terminate, precisely as in some species of Cladodus. None 

 of the specimens show the entire length of the median denticle, 

 but it was apparently long and slender. 



Formation and locality. Upper Devonian; Elmhurst, Illinois. 

 Genus PHOEBODUS St. John and Worthen. 



Teeth differing from those of Diplodus in having three prin- 

 cipal cones of about equal size, and from one to three very small 

 intermediate cones. 



