204 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



little, short, flattened, spine-like appendages protruding from these 

 furrows, with an outward imbricating arrangement or inclination 

 towards the extremities of the rays. There may have been other 

 little spines over the outer surface, in addition to those fringing the 

 margins of the disk, though the specimens retain no traces of them." 



Genoholotype. — S. Jlmbriatus Meek and Worthen. Lower Carbonif- 

 erous (St. Louis) of Illmois. 



The other three species referred to Scho^naster probably do not be- 

 long in this genus. The specimens have not been studied. 



SCH(ENASTER FIMBRIATUS Meek and Worthen. 

 Plate 35, figs. 1-4. 



Palxasterina (Schoenaster) Jimbriata Meek and Worthen, Proc. Acad. Nat. ScL, 



Philadelpliia, vol. 12, 1860, p. 449. 

 Schoenaster Jlmbriatus Meek and Worthen, Geol. Surv. Illinois, vol. 2, 1866, 



p. 278, pi. 19, figs. 7a-7d. 



Original description. — "Body regularly pentagonal star-shaped, 

 with the rays produced into rather acutely pomted arms, which are 

 convex above, and about equal in length to the diameter of the disk. 

 Plates of the upper side of the arms and disk, convex, or even tumid ; 

 near the disk those of the rays hexagonal, heptagonal, or irregular 

 m form, alternating, and consisting of about five or six longitudinal 

 rows, with a few much smaller intermediate pieces. Farther out 

 the rays, they gradually pass into two mesial ranges of oblong, alter- 

 nating pieces, with their longer diameter parallel to that of the rays; 

 while on each side of these, minute irregular pieces fill the space 

 between them and the marginal pieces. Toward the extremities 

 of the rays, these little intermediate pieces diminish in size and at 

 last become obsolete, leaving only the two middle and outer, or adam- 

 bulacral rows. Ambulacral furrows, in apparently undistorted 

 specimens, deep and nearly or quite twice as wide as the row of 

 pieces on either side; adambulacral pieces rather thick and strong, 

 and liable to present considerable differences in their obliquity and 

 breadth of surface exposed, in consequence of the compression or 

 distortion of the specimen. Plates of the under side of the disk, very 

 much smaller than the adambulacral, closely crowded together, 

 and owing to their imbricating arrangement, presentmg much the 

 appearance of the scales of a fish; immediately on each side of the 

 rays, they imbricate toward the latter, but near the middle of the 

 space between any two ambulacra, the imbrication is inward toward 

 the mouth, so that in tracing the rows parallel to their longer diam- 

 eter, across between the rays, they are found to describe a nearly 

 semicircular curve, with a slight angularity near the middle. 



"Near the extremities of the rays, the dorsal pores are seen to 

 pass between the ends of the two mesial ranges of oblong pieces, 



