KEVISION OF PALEOZOIC STELLEKOIDEA. 173 



quincunx. The radial and supramarginal columns may be dis- 

 cernible in somewhat larger plates. Adambulacrals many, like coins 

 set on edge. * 



Contains: 



Urasterella McCoy 



Genus URASTERELLA McCoy (emend.). 

 Plates 27 to 30. 



Urasterella McCoY, British Pal. FOBS., 1851, p. 59 (not defined). HALL, Twentieth 

 Kept. N. Y. State Cab. Nat. Hist., 1868, p. 289; rev. ed., 1868=1870, p. 332. 

 McCoY, Geol. Surv. Victoria, dec. 1, 1874, p. 42. ZITTEL, Handb. Pal., 

 vol. 1, 1879, p. 453. STURTZ, N. Jahrb. fur Min., etc., 1886, vol. 2, p. 152; 

 Palseontographica, vol. 36, 1890, p. 219. GREGORY, Geol. Mag., dec. 4, vol. 6, 

 1899, p. 352. 



Stenaster BILLINGS (part), Geol. Surv. Canada, Can. Org. Rem., dec. 3, 1858, 

 p. 77. STURTZ, Verh. naturh. Ver. preuss. Rheinl., etc., vol. 50, 1893, 

 pp. 40, 56. 



Eoemeraster STURTZ, Palaeontographica, vol. 32, 1886, p. 85 (genoholotype, Asterias 

 asperula Roemer); vol. 36, 1890, p. 220; Verh. naturh. Ver. preuss. Rheinl., 

 etc., vol. 50, 1893, pp. 52, 73. 



Protasteracanthion STURTZ, Palseontographica, vol. 32, 1886, p. 90 (genoholotype, 

 P. primus Stiirtz= Asterias asperula Roemer); Verh. naturh. Ver. preuss. 

 Rheinl., etc., vol. 50, 1893, pp. 54, 75. 



Palasteracanthion STURTZ, N. Jahrb. fur Min., etc., 1886, vol. 2, p. 153 (genoholo- 

 type, "A, primus "= Asterias asperula Roemer). STURTZ, Verh. naturh. Ver. 

 preuss. Rheinl., etc., vol. 50, 1893, p. 75. 



Salteraster STURTZ, Verh. naturh. Ver. preuss. Rheinl., etc., vol. 50, 1893, pp. 

 43, 60 (genoholotype, Palseaster asperrima oalter). 



fEoactis SPENCER, Mon. Brit. Pal. Asterozoa, pt. 1 (Palseontogr. Soc. for 1913), 

 1914, p. 30 (genoholotype, E. simplex Spencer=? Urasterdla girvanensis). 



Generic characters. Disk very small, without interbrachial arcs. 

 Rays five, very long and slender at maturity, but shorter and rapidly 

 tapering when immature. 



Abactinal side with very numerous small stellate plates, all of 

 which, excepting one or three medial columns, are drawn out into 

 more or less long, blunt, stout, erect, nonarticulating rods. The disk 

 is occupied by a central plate and a first ring with five plates, which 

 in some species are seen to be the basal radial plates, followed by a 

 second ring with 1 5 plates. Five of the latter are the second proximal 

 radial plates, and 10, basal plates of the supramarginal columns. 

 Between the central plate and the first ring there may be inserted a 

 few accessory, much smaller pieces. These disk ossicles may remain 

 more prominent throughout life or may have the size of the other 

 abactinal plates, in which case their arrangement is not plainly made 

 out. In the center of the ray the adial column may be the more 

 conspicuous throughout life or it may be more or less completely 

 suppressed when the supramarginals adjoin and these may then 



