604 



PISCES. 



[ORT. I'AI.. 



FIG. 1153. Orodus 

 variabilis. 



turgidus, St. John & Worthen, 1875, Geo. 

 Sur. 111., vol. 6, p. 310, Kaskaskia Gr: 

 variabilis, Newber- 

 ry, 1875, Ohio 

 Pal., vol. 2, p. 50, 

 Waverly Gr. 

 variocostatus, St. 

 John & Worthen, 

 1875, Geo. Sur. 

 111., vol. 6, p. 304, 

 Burlington Gr. 

 whitii, St. John & Worthen, 1875, Geo. 

 Sur. 111., vol. 6, p. 297, Waverly or 

 Kinderhook Gr. 



ORTHACANTHUS, Agassiz, 1843, Poiss. Foss., 

 t. 3, p. 330, [Ety. orthos, straight ; 

 akantha, spine.] Spines straight or 

 ge"ntly curved ; two or more rows of 

 denticles on the posterior face. Type 

 O. cvlindricus. 



FIG. 1154. Orthacanthus gracilis. 



arcuatus, Newberry, 1857, (Pleuracanthus 

 arcuatus,) Proc. Acad. Nat. Sci. Phil., 

 p. , and Ohio Pal., vol. 1, p. 332, Coal 

 Meas. 



gracilis, Newberry, 1875, Ohio Pal., vol. 

 2, p. 56, Coal Meas. 



quadriseriatus, Cope, 1877, Pal. Bull. No. 

 26, in Proc. Am. Phil. Soc., vol. 17, p. 

 192, Permian. 



ORTHOPLEURODUS, St. John & Worthen, 1883, 

 Geo. Sur. 111., vol. 7, p. 190. [Ety. 

 orthos, straight ; pleuron, side ; odous, 

 tooth ; in allusion to the straight pos- 

 tero-lateral border of the maxillary 

 posterior tooth.] Posterior teeth of 

 upper jaw subspatulate in outline ; 

 postero-lateral border straight, or nearly 

 BO, and probably gently curved down- 

 ward and inward at the outer ex- 

 tremity, and gently arched in the same 

 direction, terminating posteriorly in an 

 acute angle or spur, whence the inner 

 margin, which is greatly thickened or 

 massive, is broadly rounded into and 

 merges with the thin antero-lateral 

 border toward the extremity ; coronal 

 surface occupied by a prominent prin- 

 cipal fold or ridge rising nearest the 

 straight border, and flanked on the an- 

 terior slope by an obscure secondary 

 ridge; the punctate enamel forms a 

 narrow fold along the thickened straight 

 border; teeth supposed to have occu- 

 pied a similar position on the man- 

 dibles, distinguished by their trigonal 

 outline, somewhat strong and spiral in- 

 rollment of the extremity, toward which 

 the antero and postero-lateral borders 

 regularly converge, inner margin more 

 or less obliquely rounded, and sigmoid- 

 ally curved from front toward the 

 posterior angle ; coronal surface pre- 



senting a more or less well-defined 

 plane ; anterior fold, abruptly broken 

 down on that side, where the coronal 

 enamel forms a wide belt sharply de- 

 fined from the deep basal rim, and 

 limited behind by the more or less 

 deep longitudinal depression from 

 which rises the alate posterior lobe, 

 which is limited exteriorly by a narrow 

 fold of enamel separating the crown 

 from the basal portion of the tooth ; 

 mandibular median or second teeth 

 characterized by their triangular out- 

 line, rather strong inrollment of the 

 outer extremity ; straight postero-lateral 

 border, which is similarly enameled to 

 the antero-lateral border of last above 

 described posterior dental plates; antero- 

 lateral border rapidly and irregularly 

 converging from the subacute angle of 

 the broad, slightly arched inner mar- 

 gin ; coronal surface forming a broad, 

 low arch, or nearly plane transversely. 

 Type 0. carbonarius. 



carbonarius, Newberry & Worthen, 1866, 

 (Sandalodus carbonarius,) Geo. Sur. 

 111., vol. 2, p. 104, Up. Coal Meas. 



convexus, St. John & Worthen, 1883, Geo. 

 Sur. 111., vol. 7, p. 193, Coal Meas. 



novomexicanus, St. John & Worthen, 

 1883, Geo. Sur. 111., vol. 7, p. 195, Sub- 

 carboniferous. 



PAL^EASPIS, Claypole, 1885, Quar. Jour. Geo. 

 Soc. Lond. [Ety. palaios, ancient ; aspie, 

 shield.] Plates or scutes ornamented. 

 Only single dorsal plates discovered. 

 Type P. americana. 



americana, Claypole, 1885, Quar. Jour. 

 Geo. Soc. Lond., Up. Silurian or Low. 

 Devonian. 



truncata, Claypole, 1885, Quar. Jour. Geo. 

 Soc. Lond., Up, Silurian or Low. De- 

 vonian. 



PAL.EOBATIS, Leidy, 1856, Trans. Am. Phil. 

 Soc., vol. 11, p. 87. [Ety. palaios, an- 

 cient ; batis, a prickly kind of roach or 

 ray.] Type P. insignis. 



insignis, Ltidy, 1856, Trans. Am. Phil. 



Soc., vol. 11, p. 87, Keokuk Gr. 

 PAL.EONJSCUS, Agassiz, 1833, Recherches sur 

 les Poissons Fossiles, t. 1, p. 4. [Ety. 

 palaios, ancient ; oniscus, a wood-louse.] 

 Small, fusiform, deep between ventral 

 and pectoral fins; tail heterocercal, 

 forked, upper lobe longer and narrower 

 than lower; fins small; jaws large; 

 teeth minute ; scales rhomboidal, 

 smooth or striated. Type P. fultus. 



alberti, see Rhadinichthys alberti. 



brainerdi, Thomas, 1853, Bost Soc. Nat. 

 Hist, vol. 4, Ohio Pal., vol. 1, p. 346, 

 Berea grit. 



browni, Jackson, 1851, Rep. on Albert 

 Coal Mine, Coal Meas. 



cairnesi, see Rhadinichthys cairnesi. 



gracilis, Newberry & Worthen, 1870, Geo. 

 Sur. 111., vol. 4, p. 347, Coal Meas. 



jacksoni, Dawson, 1877, Can. Nat. Quar. 

 Jour. Sci., vol. 8, Carboniferous. 



