REVISION OF PALEOZOIC STELLEEOIDEA. 159 



Lepidaster with the recent ScytJiaster, which is made up of plates of 

 various sizes ^vithout regular arrangement. It seems more natural 

 to compare Lepidaster with Siluric and Ordovicic genera than with 

 recent forms, and particularly when nearly identical structures are 

 found in the genera mentioned. 



Forbes also describes Lepidaster as having the ambulacral grooves 

 " towards the extremity, in some instances partially filled up by small 

 polygonal intervening plates." His figures show a few of these 

 plates arranged in single columns. This anomalous structure is 

 undoubtedly best explained by accepting Stiirtz's conclusion, that 

 they are the separated ambulacral pieces, since otherwise none of 

 these plates appear to be present. As a fifth actinal, or a single 

 ambulacral column, the structure is out of all harmony with star- 

 fishes 



Genus HELIANTHASTER Roemer. 



Helianthaster Roemer, Palseontographica, vol. 9, 1863, p. 147, pi. 28. — Quenstedt, 

 Petrefactenkunde Deutschlands, vol. 4, 1876, p. 82, pi. 93, fig. 32.— Zittel, 

 Handb. Pal., vol. 1, 1879, p. 453.— Sturtz, N. Jalirb. fur Min., etc., 

 1886, vol. 2, p. 148; Palaeontogtapliica, vol. 32, 1886, p. 81; vol. 36, 1890, 

 p. 218, pi. 27; Verb, naturh. Ver. preuss. Rheinl., etc., vol. 50, 1893, pp. 12, 

 30. — Gregory, Treat. ZooL, vol. 3, Echinoderma, 1900, p. 258. — Clarke, 

 Bull. N. Y. State Mus., No. 121, 1908, p. 61, pi. 10.— Schondorf, Jabrb. nas- 

 eauiscb. Ver. Naturk., Wiesbaden, vol. 62, 1909, p. 34. 



Generic characters. — Disk large; rays 14 to 16 in the genotype. 

 Interbrachial actinal areas weU developed but not over-large for a 

 many-rayed astorid, either integumentary or granular, distally con- 

 cavely cut out and margined by several small inframarginals, about 

 seven on each side of a larger axillary piece. 



Madroporito marginal, large, more actinal than abactinal, radi- 

 ately striate, interbrachial, and situated immediately outside of the 

 inframarginals. In the fossils it appears to be of the actinal surface. 



Eays long and slender, protruding beyond the disk more than 

 twice the length inside the disk. Adambulacrals opposite one 

 another, mth small lateral spines, prominent and large, wider than 

 long, bounding the rays, and terminating proximally in pairs of 

 modified pieces. These make the adambulacral parts of the oral 

 armature. Ambulacral grooves narrow, ambulacral ossicles not 

 seen but probably arranged opposite one another. 



AbactinaUy the disk appears to have a scale-like covering. The 

 rays have median columns of radialia, outside of which are stout 

 columns of supramarginal ossicles, 



Genoholotype (typo by monotypy). — H.rhenanus Roemer (citations 

 as above). Lower Dovonic of Bundonbach, Germany. The above 

 definition is based on the illustrations of Sturtz. There is a second 

 species in Germany, and H. filiciformis occurs in England. 



50001°— Bull. 88 — 15 11 



