ee\t:sion of paleozoic stelleeoidea. 173 



quincunx. Tho radial and supramarginal columns may be dis- 

 corniblc in somowhat larger plates. Adambulacrals many, like coins 

 set on edge. 

 Contains.' 



TJrastereUa jSIcCoy. 



Genus URASTERELLA McCoy (emend.). 



Plates 27 to 30. 



Urasterella McCoy, British Pal. Foss., 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; 



Palseontograpliica, vol. 36, 1890, p. 219. — Gregory, Geol. Mag., dec. 4, vol. 6, 



1899, p. 352. 

 Stenaster Billings (part), Geol. Sui-v. Canada, Can. Org. Rem., dec. 3, 1858, 



p. 77. — STiJRTz, Verh. naturli. Ver. preuss. Rheinl., etc., vol. 50, 1893, 



pp. 40, 56. 

 Hoemeraster Stxjrtz, Palseontograpliica, vol. 32, 1886, p. 85 (genoholot}-pe, 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 (genoholotji^e, 



P. piivius StiXTtz= Asterias asperula Roemer); Verh. naturh. ^'er. preuss. 



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

 Palasteracanthion STtJRTz, N. Jahrb. fiir Min., etc., 1886, vol. 2, p. 153 (genoholo- 



type, "A. primus ^ '= Asierias asperula Roemer). — SxtiRTZ, Verh. natm'h. Ver. 



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

 Salterasier Stxjrtz, Verh. naturh. Ver. preuss. Rheinl., etc., vol. 50, 1893, pp. 



43, 60 (genoholotype, Palseaster asperrima Salter). 

 fEoactis Spencer, Mon. Brit. Pal. Asterozoa, pt. 1 (Palajontogr. Soc. for 1913), 



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



Generic characters. — Disk very small, without interbracbial 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. Tlie 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 15 plates. Five of the latter are the second j^roximal 

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

 Between the central plate and tho 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 bo more or less completely 

 suppressed when the supramarginals adjoin and these may then 



