PLEUEACANTHID^E. 
13 
1870. Diplodus compressus , 0. St. John, Proc. Amer. Phil. Soc. vol. xi. 
p. 432. 
1872. Diplodus compressus , 0. St. John, in Hayden’s Final Rep. U.S. 
Geol. Surv. Nebraska, p. 240, pi. iv. fig. 19. 
1873. Diplodus compressus , J. S. Newberry, Rep. Geol. Surv. Ohio, 
vol. i. pt. ii. p. 335. 
1875. Diplodus compressus , J. S. Newberry, op. cit. vol. ii. pt. ii. p. 45, 
pi. lviii. fig. 2. 
Type. Detached tooth. 
Teeth as large as those of D. gibbosus. Principal cusps of dental 
crown extremely compressed, divergent, with serrated edges : 
anterior median denticle comparatively long and slender. 
It is uncertain whether this supposed species is not the young of 
D. latus. 
Form, dp Loc. Coal-Measures : Indiana, Ohio, Nebraska. 
P. 1718. Two teeth : Linton, Ohio. Egerton Coll. 
Diplodus gracilisj Newberry. 
1856. Diplodus gracilis , J. S. Newberry, Proc. Acad. Nat. Sci. Philad. 
p. 99. 
1873. Diplodus gracilis , J. S. Newberry, Rep. Geol. Surv. Ohio, vol. i. 
pt. ii. p. 335. 
1875. Diplodus gracilis , J. S. Newberry, op. cit. vol. ii. pt. ii. p. 45, 
pi. lviii. fig. 3. 
Type. Detached tooth. 
Doubtfully distinct from D. compressus ; the typical teeth only 
differ from those of the latter species in the less compressed and 
more slender character of the principal cusps. 
Form, dp Loc. Coal-Measures: Ohio. 
P. 1719. Two teeth ; Linton. Egerton Coll, 
P. 3029. Another tooth ; Linton. Enniskillen Coll. 
Diplodus acinaces, Dawson. 
1860. Diplodus acinaces, J. W. Dawson, Acad. Geol., Suppl. p. 46, fig. 43. 
1878. Diplodus acinaces , J. W. Dawson, Acad. Geol., 3rd ed. p. 211, 
fig. 58. 
Type. Detached tooth. 
Teeth robust; principal cusps of the crown moderately compressed, 
without serrated edges, one much larger than the other, and only 
slightly divergent; anterior median denticle small, slender. 
Form, dp Loc. Coal-Measures : Nova Scotia. 
P. 1721. Five teeth ; Pictou, 
Egerton Coll. 
