REVISION OF PALEOZOIC STELLEROIDEA. 193 



ginal plates. The ambit al plates are very numerous, showing a dis- 

 tinct progression to far more numerous columns of plates than in 

 Urasterella. They also appear like those in this genus. It is prob- 

 able that the abactinal area when it is known will be seen to have 

 spicular ossicles like those of the ambital areas. 



COMPSASTER FORMOSUS Worthen and Miller. 



Plate 31, figs. 1, 2. 



Compsaster formosus WORTHEN and MILLER, Geol. Surv. 111., vol. 7, 1883, p. 327, 

 pi. 31, figs. 2a, 26. 



Original description. "Body deeply stellate; central disk com- 

 paratively small; rays rigid, large, fusiform, more than twice as long 

 as the diameter of the central disk, and terminating abruptly in an 

 obtuse point. The typical specimen furnishes the following meas- 

 urements: Diameter of the body, 0.72 inch; length of ray from cen- 

 tral part of disk, 1.78 inches; diameter of the ray at its junction with 

 the body, 0.41 inch. 



"Ambulacral grooves deep; ossicles rather small; adambulacral 

 plates very numerous, and consisting of series of thin plates upon 

 each side of the ambulacral furrows, which are rounded upon the 

 exterior, prolonged below, and each bear a short, sharp spine on the 

 upper part of the inner side, directed toward the apex of the ray. 

 There are about eighty adambulacrak upon each side of the furrows, 

 and they dimmish very slowly in size toward the apex, after passing 

 the fusiform enlargement of the ray. 



"The disk-plates abut upon the adambulacrals in a straight line; 

 they are subquadrangular, or polygonal, and each bears a strong 

 central spine. Six longitudinal rows appear on the ventral side on 

 each side of the ambulacral furrows; they are somewhat uniform in 

 size, arranged in transverse, as well as longitudinal order, and are 

 about two-thirds as numerous in a longitudinal row as the plates in 

 an ambulacral series. 



"Oral plates, madreporiform tubercle, and dorsal side unknown, 

 except so far as we may judge of the spinous character of the plates 

 from those visible on the ventral side. 



"This large and beautiful species is so distinct from any hitherto 

 described that no comparison is necessary for the purpose of identifi- 

 cation. 



"Position and locality. Okaw bluffs, between Chester and Kaskas- 

 kia, Randolph county, Illinois; from the second division of the Chester 

 limestone. 



"Illinois vState coUection of 1880, by A. H. Worthen, No. 2476." 



The writer has not been able to consult the type-specimen. 



