REVISION OF PALEOZOIC STELLEROIDEA. 205 



but farther in toward the disk they are more irregularly dis- 

 tributed. Our enlarged figure 7&, pi. 19, represents these pores 

 and the dorsal plates, as seen in one of the rays, with the convex 

 outer portion of the plates ground away, in which condition the pores 

 probably appear larger than natural. In specimens with the tumid 

 portion of these plates unremoved, the pores are not readily seen, 

 and the whole dorsal side then seems to be made up of solid, close- 

 fitting pieces. Greatest diameter across between the extremities of 

 the opposite rays, about 2.37 inches; diameter of disk, 1 inch; breadth 

 of ambulacral furrows, about 0.10 inch; length of little flattened 

 marginal spines, near 0.08 inch. 



" Locality and position. St. Clair County, Illinois; in the St. Louis 

 division of the Subcarboniferous series." 



The specimen has not been studied. 



SCHCENASTER (?) WACHSMUTHI Meek and Worthen. 

 Plate 33, fig. 6. 



Schcenaster wachsmuthi MEEK and WORTHEN, Proc. Acad. Nat. Sci., Philadelphia, 

 vol. 18, 1866, p. 259; Geol. Surv. Illinois, vol. 3, 1868, p. 499, pi. 17, fig. 4. 



Original description. "Body flattened or much depressed, with 

 a regular, distinctly pentagonal outline, the angles being produced 

 into five rather attenuated rays, which are a little convex above, 

 and apparently as much as two-thirds as long as the diameter of 

 the disk, if not more. Disk concave in outline on the margin be- 

 tween the rays, and imparting a slightly alate character to the 

 latter by extending a little along their margins; like the dorsal side 

 of the rays, composed above of numerous bmall, slightly convex 

 plates. Dorsal pores moderately distinct between the plates. 

 Plates of the under side of the disk about as large as those of the 

 dorsal side, but flattened, scalelike, crowded, and having the inward 

 imbricating character of the genus strongly marked. Ambulacra 

 (as seen in a compressed specimen) very narrow, their marginal 

 plates moderately large, oval-oblong, comparatively thin, and very 

 strongly imbricating outward. Between these, two rows of short, 

 flattened, spinelike scales are seen arising from the ambulacral 

 furrow, and all inclining outward or toward the extremities of the 

 rays. (Other characters unknown.) 



"Diameter of disk, 1.32 inches; rays apparently extending as much 

 as 0.90 inch or more beyond the margins of the disk. 



"This species will be readily distinguished from our 8. fimbriatus, 

 of the St. Louis limestone, the only other species of the genus known 

 to us, by its smaller and less convex plates on the dorsal side, as well 

 as by its much thinner, less oblique, and more strongly imbricating 

 row of plates along each side of the ambulacra, and particularly 

 by its much narrower ambulacral furrows. We have not seen any 



