DEVONIC FISHES OF THE NEW YORK FORMATIONS l6l 



conical and well separated, except those of the two anterior ridges, which 

 are coalesced and worn on their summits. Total length of plate 3 cm. 



This species, like the preceding, is founded upon a unique dental plate 

 from the Cedar Valley limestone of Iowa. It comes, however, from a 

 higher level, locally known as the " Euomphalus bed," which lies about 

 eight feet below the summit of the Middle Devonic in Muscatine county. 



Formation and locality. Cedar Valley limestone ; Fairport, la. 

 Dipterus costatus Eastman 



Plate 4, figure g 



1900 Dipterus costatus C. Ji. Eastman. Jour. Geol. 8: 39, text fig. 4 

 Dental plates agreeing in size and general outline with D. calvini, 

 but with fewer and more widely separated coronal ridges, which disappear 

 before reaching the middle of the plate. The distinguishing feature of this 

 species consists in the elevated acute ridge extending along the entire 

 length of the inner border, and separated from the remaining tuberculated 

 ridges by a broad longitudinal furrow. This ridge appears to be made up 

 of three coalesced costae, of which the third counting from the inner margin 

 is the largest. The two innermost costae are so faint as to be almost 

 imperceptible against the steep face of the main ridge. The latter shows 

 no evidence of having been tuberculated, although faint and partially 

 coalesced tubercles occur on the five remaining costae. Several examples 

 of this species, including the type, are preserved in the Museum of Com- 

 parative Zoology at Cambridge, Mass. 



Formation and locality. State Quarry beds (Upper Devonic) ; near 

 North Liberty, JohnsOn co., la. 



Dipterus mordax Eastman 



Plate 4, figures 5, 6 



1900 Dipterus mordax C. R. Eastman. Jour. Geol. 8: 39, text fig. 6, 8 



Lower dental plates attaining a length of over 3 cm, coronal surface 



gently convex, with six rows of very large, discrete, conical or rounded 



tubercles which extend from the outer margin for a variable distance toward 



the posterior angle ; the two posterior rows often rudimentary. Some of 



