THE DEVONIAN FISHES OF MISSOURI 61 



liar on account of a strong longitudinal ridge along the entire 

 length of the lower side in the median line. On either side of 

 this ridge there are deep, wide depressions, from each of which 

 rises a round-topped projection like a truncated cone. On the 

 upper surface three shallow depressions distinguish it from 

 described forms. (Fig. 1). 



The external occipital, like that of D. intermedius, pro- 

 jects little behind the occipital, but it is unusual in its very 

 short articulation with that bone. The length of this articu- 

 lation is shown in the left margin of figure 4. (Fig. 4). 



Only a small part of the dorso-median is preserved but 

 its size and association indicate that it belongs to this species. 

 (Fig. 2). 



Formation and locality : Near the top of the Devonian at 

 Louisiana, Mo. Collection of Mr. Rowley. 



Dinichthys missouriensls sp. nov. 

 (Plate II, figs. 1, 2, and 4. Plate III, fig. 1) 

 The lower end of the left upper dental plate is missing. 

 The length preserved is 109 mm. but its total length was at 

 least 160 mm. The greatest width of the cutting blade is 62 

 mm. The cutting blade is thin but has a prominent rounded 

 ridge 9 mm. high, 20 mm. back of the front edge. The shape 

 of its cross section as shown in text figure 1 distinguishes it 

 from all other described species. (Fig. 1). 



Text figure 1. Cross section of left upper dental plate of Dinichthys 

 missouriensis. 1, Outer view of tooth; 2, Ridge near front edge. 



Only the posterior part of the mandible is preserved. It 

 is 13 cm. wide compared to 7 cm. for D. rowleyi, and is propor- 

 tionately thick. If found in the Cleveland shale of northern 



