250 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Distribution. — Known only from the type-locality. 



Remarks. — This species agrees with /**. symholious in having the 

 snperomarginals of tlie ray, except the last two or three, separated 

 by a single series of abactinal plates, but differs in having conspicu- 

 ously tumid marginal plates, the distal half dozen of each series 

 bearing a small central tubercle. The furrow spines are 4 or 5 in- 

 stead of 8 to 12, and the species is small while syrribolicus is large. 



ROSASTER MIMICUS Fisher. 



Plate 62, fig. 1 ; plate 65, fig. 1 ; plate 70, fig. 1 ; plate 91, figs. 4, 4a^Z>. 

 Rosastcr mimicus Fisher, 1913a, p. 632. 



Diagnosis. — Resembling somewhat R. hij/unctus (Sladen), but dif- 

 fering in having sharper rays, compacter paxillae with numerous 

 crowded central granules, more numerous, compressed, furrow spines 

 (12 to 14), more numerous subambulacral spines and granules, and 

 more numerous oral spines. Form stellate with arcuate interbrachia 

 and gradually tapering rays; sides of ray and disk perpendicular 

 v.ith a longitudinal depression : breadth of ray, measured at proximal 

 suture of first pair of superomarginals which meet medially equal to 

 first 3.5 or 4 superomarginals measured on ambitus ; abactinal plates 

 strongly tabulate on papular areas and with upward of 23 central and 

 25 peripheral granules on the radial series; abactinal, marginal, ac- 

 tinal intermediate, and adambulacral pedicellariae: subambulacral 

 armature a series of prismatic spines and 2 or 3 parallel series of 

 granules; furrow spines 12 to 14. R=:56 mm., r=21 mm., 11=2.7 r 

 (cotype) ; in type R=probably T5 mm. and r=23 mm. 



Description. — The general form is sufficientl}'^ shown by the pho- 

 tographic figure. The raj^s are only of moderate length, the tip of 

 all of those of the type being missing, but the slightly smaller cotype 

 has a perfect ray. Abactinal area stellato-pentagonal to pentagonal. 

 Abactinal plates regular, those of the radial areas and center of disk 

 (papular area) strongl}^ tabulate, a radial and 3 parallel longitudinal 

 series being S3anmetrically hexagonal, flat-topped, or slightl}'^ convex. 

 A radial plate of the type has upward of 23 subcircular or polygonal 

 fhit.-topped or slightly convex depressed central granules, and 15 to 

 25 truncate larger periplieral ones, the outer edges conforming to 

 the contour of the pentagonal form as if dressed Avitli a Imife. The 

 jn'oximal plates have the largest and fewest peripheral granules. In 

 the cotype (station 5282) the peripheral granules of the radial series 

 range from 12 to 18 and the central, 8 or 9 to 12. The plates on 

 center of disk are irregularly hexagonal or pentagonal Avith clean-cut 

 edges. The primary basal plates are slightly larger than the largest 

 radial plates. There are 5 or 6 chevrons of close-set, four-sided, in- 

 terradial plates covered with a uniform mail of oblate spherical gi*an- 



