38 C. R. EASTMAN 
There is a progressive diminution in size of all denticles pro- 
ceeding posteriorly. The coronal surface is finely punctate. 
This beautiful dental plate is the oldest of all Depterus remains 
that have been found in this country. It was discovered by 
Professor J. A. Udden of Augustana College, Rock Island, in 
Fic. 4. Diplerus costatus sp. nov. Upper Devonian ; Johnson county, lowa. 
Fics. 5, 5%. Dipterus uddeni sp. noy. Cedar Valley limestone; New Buffalo, 
lowa. 
Fics. 6, 8. Dipterus mordax sp.nov. Upper Devonian; Johnson county, Iowa. 
Fic. 7. Dipterus calvinit sp. nov. Cedar Valley limestone ; Fairport, lowa. 
whose honor the specific title is dedicated. A note of its geo- 
logical occurrence was published in the August number of this 
JouRNAL (p. 494) for last year. 
2. D. calvini, sp. nov. (Fig. 7).—Like the last, this species 
is founded on a unique dental plate (right mandibular) from the 
Cedar Valley limestone of Iowa. It comes from a higher level, 
