PLEURACANTHIDiS. 
3 
Aganodtis, Ochhdut, and Pternodug, according to Hancock and 
Atthey are supposed genera founded upon fragments of the teeth 
named Diplodus. Didgmodus must also be included here until 
satisfactory evidence as to its true position is obtained ; the dis- 
tinctive features noted by Prof. Cope * are most probably due to the 
perfection of the Texas fossils as compared with those of Europe. 
The teeth of most species of Pleuracanthus cannot yet be corre- 
lated with the spines, and it is thus necessary stiU to retain the 
provisional name of Diplodus. 
I. Species already Icmwn with much completeness. 
Pleuracanthus decheni (Goldfuss). 
1847. Orthacanthus decheni, Goldfuss, Neues Jahrb. p. 404. 
1847. Orthacanthus decheni, Goldfuss, Beitr. vorw. Fauna Steink. p. 23, 
pi. v. figs. 0-11. 
1848. Xenacanthus decheni, E. Beyrich, Monatsh. Verb. k. Preuss. 
Akad. Wiss. p. 24. 
1840. Triodus sessUis, Jordan, Neues Jahrb. p. 843. 
1851-66. Xenacanthus decheni, F. Koemer, in Bronn's Letb. geogn. 
3rd ed. vol. i. p. C03, pi. ix*. fig. 15. 
1856. Xenacanthus decheni, Schnur, Zeitscbr. deutsch. geol. Ges. 
vol. viii. p. 642. 
1857. Xenacanthus decheni, F. Roemer, Zeitscbr. deutsch. geol. Ges. 
vol. ix. p. CO. 
1857. Pleuracanthus decheni, Sir P. Egerton, Ann. Mag. Nat. Hist. [2] 
vol. XX. p. 423. 
1861. Xenacanthus decheni, H. B. Geinitz, Byas, p. 23, pi. xxiii. fig. 1. 
1867. Xenacanthus decheni, R. Kner, Sitzungsb. k. Akad. Wiss. Wien, 
vol. Iv. pt. i. p. 640, pis. i.-x.’ 
1808. Xenacanthus decheni, C. Liitken, Geol. Mag. vol. v. p. 376. 
1880. Pleuracanthus decheni, J. W. Davis, Quart. Joum. Geol. Soc. 
vol. xxxvi. p. 321. 
1883. Pleuracanthus and Xenacanthus, C. Ilasse, Neues Jahrb. vol. ii. 
p. 65. 
Type. Imperfectly preserved skeleton ; Berlin Museum. 
A comparatively small species, the barbed spine not attaining a 
greater length than about 0-11 m. in the adult. Spine much 
compressed and flattened antero-posteriorly ; denticles thick, pointed 
hut not hooked, placed in very clo.se series upon each lateral margin. 
Principal cones of the dental crown compressed, smooth or slightly 
striated, with a slender intermediate denticle. 
‘ Nat. Hist. Trans. Northumb. & Durham, vol. iii. p. 113. 
’ See detailed description in Proc. Amer. Phil. Soc. 1884, pp. 572-590, plate. 
’ This is the most exhaustive account of the genus and species yet published. 
B 2 
