PLEURACANTHID^. 13 
1870. Diplodiis compresstis, O. St. John, Proc. Amer. Phil. Soc. vol. xi. 
p. 432. 
1872. Diplodus cotnprestug, O. St. John, in Hayden’s Final Rep. U.S. 
Geol. Surv. Nebraska, p. 240, pi. iv. fig. 19. 
1873. Diplodus compressm, 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. 4.5, 
pi. Iviii. fig. 2. 
Type. Detached tooth. 
Teeth as large as those of D. gihhosus. 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. lotus. 
Form. ^ Loe. Coal-Measures : Indiana, Ohio, Nebraska. 
P. 1718. Two teeth; Linton, Ohio. Egerton Coll. 
Diplodus gracilis, Newberry. 
1866. Diplodus graoilis, 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. Iviii. fig. 3. 
Type. Detached tooth. 
DoubtfuUy 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. ^ Loc. Coal-Measures : Ohio. 
P. 1719. Two teeth ; Linton. Egerton Coll. 
P. 3029. Another tooth ; Linton. EnnisTciUen 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., Sided, p 211. 
fig. 58. ’ V , 
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. 4r Loe. Coal-Measures : Nova Scotia. 
P. 1721. Five teeth ; Pictou. 
Fjgerton Coll. 
