REVISION OF PALEOZOIC STELLEROIDEA. 65 



radial plates are much more decidedly ornate. Each of the supra- 

 and inframarginal columns has 14 plates against 9 in H. incomptus, 

 and of adambulacrals there are not less than 24 in a column against 

 18 to 22 in the same form. All of the ossicles are as strongly papillose 

 but not more so than in H. incomptus. The detail of the disk is not 

 determinable. 



HUDSONASTER BATHERI, new species. 

 Plate 3, fig. 3. 



Tetraster wyville-thomsoni NICHOLSON and ETHERIDGE (part), Mon. Silurian 

 Foss. Girvan Dist., Ayrshire, fasc. 3, 1880, p. 324, pi. 21, figs. 1, 2 (not the 

 other figs.). 



A small Hudsonaster. R = 6 mm., r = 2.7 mm. The largest 

 specimen: R = 8 mm. 



Actinal side only known. Inframarginal columns the largest, 

 with 8 or 9 distinctly tuberculate plates. Inside of these are 

 the columns of narrower and slightly shorter adambulacrals that 

 lie somewhat below the level of the inframarginals ; there are 

 10 or 11 of these plates bounding the ambulacral grooves, and the 

 pieces of adjacent columns are opposite or nearly opposite one 

 another. The ambulacral grooves are very narrow and deep and 

 no ambulacralia are discernible. 



Formation and locality. Dr. F. A. Bather made wax squeezes 

 for the writer from three natural molds in the collection of Mrs. 

 Robert Gray, Edinburgh; the originals are from the Upper Ordovicic 

 of Thraive, Girvan District, Scotland. The holotype is the specimen 

 illustrated as above cited. 



Remarks. Nicholson and Etheridge confused at least one of these 

 specimens with their Tetraster wyville-thomsoni , a species of totally 

 different construction, a cryptozonian, described elsewhere in this 

 work. Actinally the new species is in harmony with Hudsonaster 

 and although the abactinal side is unknown, it is thought that it 

 will be found to be like that in H. matutinus. 



Cat. No. 60601, U.S.N.M. 



Genus SILURASTER Jaekel. 

 Text fig. 6. 



Siluraster JAEKEL, Zeits. geol. Ges., vol. 55, 1903, Protokol, p. 13 (106), figs. 2, 

 3, on p. 108. SPENCER, Mon. Brit. Pal. Asterozoa, pt. 1 (Palaeontgr. Soc. for 

 1913), 1914, p. 18. 



Description. "A typical asterid with opposite ambulacralia and 

 with well-developed marginalia, therefore a true form of Phanero- 

 zonia. The strongly folded madreporite lies dorsally in an inter- 

 radius." 



