REVISION OF PALEOZOIC STELLEROIDEA. 67 



Genus PALSEASTER Hall (emend.). 

 Plate 7, figs. 1-4. 



Palseaster HALL, Nat. Hist. N. Y., Pal., vol. 2, 1852, p. 247; Twentieth Rep. N. Y. 



State Cab. Nat. Hist., 1868, p. 282; rev. ed., 1868=1870, p. 324. ZITTEL, 



Handb. Pal., vol. 1, 1879, p. 452. 

 Palseaster NICHOLSON and ETHERIDGE (part), Mon. Silurian Foss. Girvan Dist., 



Ayrshire, fasc. 3, 1880, p. 319. 

 (Not Palseaster SALTER, Ann. Mag. Nat. Hist., ser. 2, vol. 20, 1857, p. 323= Uras- 



terella.) 

 (Not Palseaster of most AUTHORS.) 



Generic characters. Disk small and without distinct interbrachial 

 arcs. Rays five and slender. 



Abactinal area of disk centrally occupied by a large plate, then a 

 ring of 5 separated, somewhat smaller, radially situated ossicles, 

 and inside the axillary pieces there are 5 subtriangular interradial 

 plates, against which lie 10 very large and conspicuous proximal 

 supramarginal plates. Between the central, radial, and interradial 

 plates are numerous small accessory pieces which separate the pri- 

 mary ossicles one from another. These accessory plates also continue 

 to crowd from the disk into the rays between the supramarginals, 

 and thus take the place of the radial columns, but are absent in the 

 distal third of the rays. Each ray has therefore 4 conspicuous 

 columns of plates, the 2 supramarginals situated inwardly of the 

 2 marginal inframarginals. The former columns terminate in 10 

 very large proximal plates situated in the axils of the disk, while the 

 inframarginals rest against the 5 very large actinal axillary margi- 

 nal pieces. All of the large plates are centrally smooth, bordered by a 

 pustulose area. 



Madreporite abactinal, of medium size, circular in outline, and 

 radially striate. It lies on top of two proximal supramarginal plates 

 and the adjoining interradial plate. 



Inframarginal plates thick and large, about as many in a column 

 (13) as in those of the supramarginals (13 or 14). The latter do 

 not completely overlie the inframarginals, since these bound the 

 rays both actinally and abactinally. The inframarginal plates, like 

 the plates of the abactinal area, have each a large, smooth, central 

 space encircled by a pustulose area. From their inner sides articu- 

 late short, thick, blunt spines, of which there are apparently not 

 more than 2 to each inframarginal plate. 



Axillary marginal plates large, hexagonal, one in each axil and 

 common to both sides of the disk axils. 



Adambulacral plates small, tumid, alternating in the main with 

 the inframarginal plates throughout the distal two-thirds of the rays, 

 but toward the mouth there are a few more adambulacrals than in- 

 framarginals. (In the type-specimen there are 13 of the latter in a 

 column to 16 of the former.) Oral armature consists of at least 5 

 pairs of drawn out and pointed basal adambulacrals. Along the inner 



