PEI;. PET.] 



PISCES. 



605 



leidyanus, Lea, 1853, Jour. Acad. Nat. 



Sci., 2d ser., vol. 2, Coal Meas. 

 modulus, see Rhadinichthys modulus, 

 peltigerus, Newberry, 1857, (Elonichthys 



peltigerus,) Proc. Acad. Nat. Sci., vol. 



8, p. 98, and Ohio Pal., vol. 1, p. 345, Coal 



Meas. 



FIG. 1155. Palseoniscus peltigerus 



scutigerus, Newberry, 1857, Proc. Acad. 



Nat. Sci. Phil., Coal Meas. 

 PELTODUS, Newberry & Worthen, 1870, Geo. { 

 Sur. 111., vol. 4, p. 362. [Ety. pelte, a ! 

 half-moon shield; odous, tooth.] Teeth | 

 small and low, round oval or elliptical | 

 iu outline, arched above in both direc- i 

 tions, concave or flattened below ; I 

 crown surface most strongly arched i 

 from front to rear, highest near the an- 

 terior margin ; more or lees evenly 

 punctate throughout; under surface 

 bony and rough ; margins thin and ir- 

 n'gular where the teeth are separated, 

 thickened and even along the lines of 

 contact when closely set. They are 

 less flat, smooth and pavement-like 

 than Psammodus, and less convoluted 

 than Cochliodus. Type P. unguiformis. 



plicomplialus, St. John & Wortben, 1875, 

 Geo. Sur. 111., vol. 6, p. 411, Kaskas- 

 kia Gr. 



quadratus, St. John <fe Worthen, 1875, 

 Geo. Sur. 111., vol. 6, p. 410, St. Louis Gr. 



transversus, St. John & Woithen. 1875, 

 Geo. Sur. 111., vol. 6, p. 412, Coal Meas. 



unguiformis, Newberry & Worthen, 1870, 

 Geo. Sur. 111., vol. 4, p. 363, Coal Meas. 

 PEPLORHINA, Cope, 1873, Proc. Acad. Nat. 

 Sci. Phil., p. 343. [Ety. peplos. a robe; 

 Rhine, a kind of dog-fish.] Type P. 

 anthracina. 



anthracina, Cope, 1873, Proc. Acad. Nat. 

 Sci. Phil., p. 343, Coal Meas. 



arctata, Cope, 1877, Proc. Am. Phil. Soc., 



p. 55, Permian Gr. 



PERIPLECTRODUS, St. John & Worthen, 1875, 

 Geo. Sur. 111., vol. 6, p. 324. [Ety. peri, 

 nearby; Plectrodus, a genus.] Base ex- 

 panded laterally or compressed ; sym- 

 metrically inrolled from within out- 

 ward, inferior surface excavated ; crown 



consisting of transverse, strong, median 

 cusps, flanked by denticles; one on 

 either side, and then regularly increase 

 in size from the outer to the inner ex- 

 tremity or with age ; coronal cusps en- 

 ameled, smooth or vertically striated. 

 Type P. warreni. 



compressus, St. 

 John & Wor- 

 then, 1875, Geo. 

 Sur. 111. vol. 6, 

 p. 326, St. Louis 

 Gr. 



expansus, St. 

 John & Wor- 

 then, 1875, Geo. 

 Sur. 111., vol. 

 6, p. 327, Kas- 

 kaskia Gr. 

 warreni, St. John 

 & Worthen, 

 1875, Geo. Sur. 

 III., vol. 6, p. 

 325, Burlington 

 Gr. 



PERIPRISTIS, Agas- 

 siz, 1870, Proc. 



Am. Phil. Soc., vol. 11, p. 434. [Ely. peri, 

 around ; pristis, saw.] Small, crown com- 

 pressed, acuminate, serrate, curved lat- 

 erally ; coronal cavity ; 

 root as in Petalodus, 

 crown and coronal cav- 

 ity covered with ga- 

 noine. Type P. semicir- 

 cularis. 



semicircularis, Newberry FlG no6Peri- 

 & Worthen, 1866, (Cten- pristis seinicir- 

 optychius semicircu- cularls. 

 laris,) Geo. Sur. 111., vol, 2, p. 72, Coal 

 Meas. 



PETALODUS, Owen 1840, Odontography, p. 

 60. [Ety. petalos, spread out; odous, 

 tooth.] Teeth transversely elongated, 

 compressed, thin, petal-shaped, cutting 

 edge serrated ; base of crown with 

 imbricating folds of enamel, descending 

 lower on the posterior than anterior 

 face ; root large, oblong, truncated be- 

 low; lower edge ob- 

 tuse, tumid. Type 

 P. hastingsi. 

 alleghaniensis, Leidy, 

 1856, Jour. Acad. 

 Nat. Sci., 2d series, 

 vol. 3, p. 161, and 

 Geo. Sur. 111., vol. 

 2, p. 35, Coal Meas. 

 curtus, Newberry & 

 -Worthen, 1866,Geo. 

 Sur. 111., vol. 6. p. 

 355, Keokuk Gr. 

 destructor, Newberry 

 1157.-Petalodus & Worthen 1866, 

 alleghaniensis. syn. for P. allegha- 



niensis. 



hybridus, St. John & Worthen, 1875, 

 Geo. Sur. 111., vol. 6, p. 394, St. 

 Louis Gr. 



