pisces. 129 



any other described species. Apparently some diminution in number of tubercles, coin- 

 cident with increase in size, takes place in the teeth of adult or old individuals. 



Upper dental plates of the D. flabelliformis type do not differ materially from the 

 lower as regards outline, or size and number of tuberculated ridges, but their sub- 

 stance is usually much thinner, the functional surface is nearly or quite plane or in some 

 cases even concave, and in the effete condition it becomes worn down almost perfectly 

 smocth. In well-preserved specimens the marginal contour is seen to be ovoid or sub- 

 triangular, like that of the lower dental plates, but the majority of examples have the 

 external margin deficient, owing to wear, injury or poor preservation, and accordingly 

 in that respect present deceptive appearances." 



Remarks — Only one specimen from the Devonian of Missouri has been collected 

 It is slightly broken on the thin margin and measures 11 mm. in length by 8 mm. in 

 width. The specimen might with equal propriety be referred to Dipterus pectinatus 

 Eastman, and the reference is made to D. mordax in the belief that the D. pectinatus 

 Eastman is a synonym of D. mordax. As teeth of species of Dipterus show considerable 

 variation the scarcity of specimens of D. pectinatus Eastman makes the species seem 

 of doubtful value. 



Occurrence — Callaway limestone of Montgomery County. 



Unidentified fish remains 



Plate 31, figures 4, 5, 6 



From Mineola, Callaway and Snyder Creek formations the writer has collected 

 fragments of plates belonging to Dinictithyids but too fragmentary to allow determina- 

 tion of the plates. Several species of armored fishes were present in each of the forma 

 tions. 



