272 



ECHINODERMA TA. 



[PLA. 



Bhumardanus, Hall, 1858, Geo. Sur. Iowa, 

 vol. 1, pt. 2, p. 532, Burlington Gr. 



siluricus, Hall, 1879, Desc. New Spec. 

 Foss., p. 9, and llth Rep. Geo. Sur. 

 Ind., p. 256, Niagara Gr. 



FIG. 397. Platycrinus scobina. Diagram. 



Btriobrachiatus, Hall, 1861, Desc. New 

 Crinoidea, p. 4, and Bost. Jour. Nat. 

 Hist., vol. 7, p. 287, Burlington Gr. 



subspinosus, Hall, 1858, Geo. Sur. Iowa, 

 p. 536, Burlington Gr. 



subspinulosus, Hall, 1860, Supp. to Geo. 

 Sur. Iowa, p. 81, Burlington Gr. 



symmetricus, Wachsmuth & Springer, 

 (in press,) Geo. Sur. 111., vol. 8, p. 186, 

 Waverly or Kinderhook Gr. 



tennesseensis, see Marsupiocrinus tennes- 

 seensis. 



tentaculatus, see Marsupiocrinus tentacu- 

 latus. 



tenuibrachiatus, Meek & Worthen, 1869, 

 Proc. Acad. Nat. Sci. Phil., p. 16, and 

 Geo. Sur. 111., vol. 5, p. 450, Burling- 

 ton Gr. 



truncatulus, Hall, 1858, Geo. Sur. Iowa, p, 

 538, Burlinu-ton Gr. 



truncatus, Hall, 1858, Geo. Sur. Iowa, p. 

 537, Burlington Gr. 



tuberosus, Hall, 1858, Geo. Sur. Iowa, p. 

 534, Burlington Gr. 



verrucopus, White, 1863, Jour. Bost. Soc. 

 Nat. Hist., vol. 7, p. 502, Burlington Gr. 



vexabilis, White, 1875, U. S. Sur. W. 

 100th Meridian, vol. 4, p. 81, Sub. Carb. 



wortheni, Hall, 1858, Geo. Sur. Iowa, p. 

 530, Burlington Gr. 



yandelli, Owen & Shumard, 1850, Jour. 

 Acad. Nat. Sci., 2d ser., vol. 2, p. 58, 

 Burlington Gr. 



PLATYCYSTITES, n. gen. [Ety. platys, flat; 

 kustit, bladder.] General form com- 

 pressed elliptical, or like the kernel of 

 a peach-seed, with a narrow rim on the 

 border; axial canal passes down into 

 the column ; three plates in the first 

 range, one of them bending around the 

 rim and the other two having the di- 

 viding suture in the rim itself ; there are 

 five large plates in the second range, and 

 above these there are three large plates, 

 on the azygous side, with six or more 

 smaller ones on the border ; the whole 

 surface is granular and every plate full 

 of minute pores. Type P. faberi. 



faberi, n. sp. Basal plates hexagonal, 

 longer than wide, one of them bending 

 around the bordered rim, and the other 

 two uniting at the middle of the rim ; 

 a large subcentral hexagonal plate in 

 the second range on the azygous side 

 rests upon the upper side of the plate, 

 which is separated by a suture in the 

 rim from an adjoining basal plate, but 

 does not reach the other basal ; this 

 large hexagonal plate joins two plates 

 in the second range with its under slop- 

 ing sides ; three large plates rest upon 

 the three upper faces of this large hex- 

 agonal plate ; the one upon the superior 

 face is octagonal, resting between the 

 other two large plates and having five 

 smaller ones joining its upper faces. 

 The specimen is worn at the upper edge 

 so as to destroy the 

 orifices. It was re- 

 ceived by Charles Fa- 

 ber among a lot of 

 fossils from the Kas- 

 ' kaskia Group in the 

 southern part of West 

 Virginia, but as no cys- 

 tideans have ever been 

 found above the Lower 

 Devonian, and as the 

 specimen is worn as if FlG - 398 - Platycys- 

 it had been drifted, the tltes faberL 

 probability is that it belongs to the 

 Silurian rocks. 



PLEUROCYSTITES, Billings, 1854, Can. Jour., 

 vol. 2, p. 250. Ety. pleuron, side ; kuslix, 

 bladder.] Body oval, flat; dorsal side 

 with large plates, ventral with smaller 

 ones; two free arms: mouth at the base 

 on the left side ; small orifice near the 

 apex; three pectinated rhombs, two 

 in the upper half and one in the 

 lower; column short. Type P. squa- 



anticostiensis, Billings, 

 1857, Rep. of Progr. 

 Geo. Sur. Can., p. 288, 

 and Can. Or*. Rem., 

 Decade 3, p. 52, Hud. 

 Riv. Gr. 



elegans, Billings, 1857, 

 Rep. of Progr. Geo. 

 Sur. Can., p. 287, and 

 Can. Org. Rem., Dec- 

 ade 3, p. 51, Trenton 

 Gr. 



exornatus, Billings, 1857, 

 Rep. of Progr. Geo. 

 Sur. Can., p. 287, Tren- 

 ton Gr. 



filitextus, Billings, 1854, 

 Can. Jour., vol. 2, p. 

 252, and Can. Org. 

 Rem., Decade 3, p. 48, 

 Trenton Gr. 



FIG. 399. Pleuro- 



cystites squamo- ro bustU8, Billings, 1854, 

 Can. Jour., vol. 2, p. 

 252, and Can. Org. Rem., Decade 3, 

 p. 49, Trenton Gr. 



