BEVISIOK OF PALEOZOIC STELLEROIDEA. 71 



the larger ossicles of both sides are centrally smooth, surrounded by 

 a finely pustulose border. 



Madreporite situated interradially and distally upon the three 

 large plates just inside an axillary marginal plate, two of which are the 

 proximal plates of supramarginal columns of adjoining rays. It is 

 circular in outline, flat, and radially striated. 



Inframarginal plates occupying the outer edges of both the actinal 

 and ab actinal areas; from 13 to 15 plates hi each column. The 

 supramarginal plates are situated above and inside the inframarginals, 

 which inwardly bear short, thick, club-shaped spines. Otherwise 

 they are ornamented like the abactinal plates. 



Adambulacral ossicles small, subquadrate, each one alternating 

 distally with an inframarginal plate, but proximally they are some- 

 what more numerous, there being from 17 to probably 20 in a column. 

 On these plates lie two series of spines the two short, thick, club- 

 shaped ones of each mframarginal plate while on the inner side of 

 each adambulacral there is inserted a linear brush of from five to seven 

 slender, short spines that are outwardly and laterally directed. 



Ambulacral grooves very narrow, deep, and gradually tapering. 

 Ambulacral plates not well seen but apparently very short, one to 

 each adambulacral and directly opposite one another. 



Axillary marginal plates five in number, very large and conspicuous 

 actmally, also showing slightly abactinally. 



Locality and formation. The only good specimen was found many 

 years ago by Col. E. Jewett in the Siluric (Rochester shale) at Lock- 

 port, New York. A fragment of the ray of a much larger individual, 

 nearly twice the size of this type, was found by the same gentleman 

 at the same place. These specimens are now in the paleontological 

 museum of Cornell University (No. 7331) and were presented by 

 Hon. Ezra Cornell. Long after the study of the form was com- 

 pleted another specimen preserving two rays and showing the actinal 

 side was learned of in the University of Toronto (Walker collection, 

 No. 1008). It was found at Grimsby, Ontario. 



Remarks. This species has never been well described nor figured, 

 and has accordingly led to endless generic confusion. Almost any 

 Paleozoic starfish with large marginal plates has been referred to 

 Pal&aster. This lack of generic conception was partially due, as 

 stated above, to the fact that the abactinal side remained unknown. 

 The specimen lies imbedded in blue shale showing the actinal area, 

 and the abactinal side was revealed by the writer by cutting away 

 the slab to the starfish and then developing the individual plates 

 with caustic potash. 



In a general way Palseaster niagarensis resembles several species but 

 all are distinguished by generic characters. The nearest one is 

 Hudsonaster incomptus from the Cincinnatic strata, but it differs at 



