90 PALEOZOIC FISHES OF NORTH AMERICA. 
which are smaller and less worn undulated, and almost but not quite tuber- 
culated. 
The best specimen in my possession was received from Prof. E. T. Nel- 
son, of Delaware, Ohio, to whom the species is dedicated. 
Formation and locality: Chemung group; Warren, Pa.; where it has 
been obtained by Mr. F. A. Randall and Mr. Charles E. Beecher. 
Diprerus (CTENODUS) FLABELLIFORMIS, Nn. Sp. 
Plate XX VII, Figs. 21, 21%. 
Teeth triangular in outline, about one inch in length, those of the upper 
jaw nearly as wide as long, forming an equilateral triangle; those of the under 
jaw twice as long as wide; crown remarkably flat; the upper teeth some- 
times slightly concave, those of the lower set gently arched; surface marked 
by eight or more radiating ridges, which continue nearly or quite to the inte- 
rior angle; the anterior ridges strongest; the middle and posterior ones set 
with rounded obtuse tubercles. 
Though having a general resemblance to some of the teeth described 
and figured by Pander and Agassiz, there are none which correspond closely 
with these in form and tuberculation. 
Formation and locality: Chemung group; Warren, Pa. Collected by 
Mr. Charles E. Beecher and Mr. F. A. Randall. 
Diererus (CTrENODUS) LEVIS, N. sp. 
Plate XXVII, Figs. 22, 23. 
Teeth triangular or oblong in outline, one inch six lines in length by 
eight lines in width; strongly arched; ridges very few, four or five in num- 
ber, all smooth, and, like the central portion of the crown, highly polished. 
The ridges are relatively short, though high, all the central portion of the 
tooth being plain. 
Of described species this most resembles Dipterus glaber Pander,” but 
in that species the ridges are acute, while in the teeth under consideration 
they are remarkably flattened. 
1 Die Ctenodipterinen der devonischens System, p. 29, pl. 7, fig. 10. 
