320 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



are long, broad, and tumid, and each bears near the suture line with 

 the siiperomarginals, a row or a group of large coarse truncated 

 spinelets." Further, the adambulacral plates have only 4 furrow 

 spines and a single " large, coarse, truncated " subambulacral spine. 

 No pedicellariae are mentioned. 



Genus ASTROTHAUMA Fisher. 



Astrothauma Fisher, 1913a, p. 645. Type, A. euphylacteum Fisher. 



Diagnosis. — Differing from Calliaster Gray in having the last 

 superomarginal plate much enlarged and in having the marginal and 

 actinal spines with a roughened or thorny surface; plates smooth, 

 bordered by a single series of granules, and with small 2- jawed 

 upright pedicellariae; marginal and actinal plates with heavy, 

 thorny, or roughened spines; prominent upright smooth or slightly 

 eroded spines on center of disk and basal portion of ray; furrow 

 spines numerous, small, in a close comb ; subambulacral spines 2 or 3," 

 large, rough, tapering, and sharp. 



ASTROTHAUMA EUPHYLACTEUM Fisher. 



Plate 86, fig. 2 ; plate 87, fig. 2 ; plate 93, figs. 7, la-c. 

 Astrothauma euphylacteum Fisheb, 1913a, p. 645. 



Diagnosis. — Rays 5. R=86 mm., r=24 mm., R=3.5-)-r; breadth of 

 ray at base, 27 mm. ; thickness of disk at interradius, 8.5 mm. Disk 

 fairly large; rays gradually tapering, rigid, blunt; abactinal plates 

 smooth, bordered by a single series of granules; center of disk and 

 proximal third of radial series with prominent, stout, sharp, upright 

 spines and a few scattered small 2-jawed pedicellariae; superomargi- 

 nals with the distalmost plate much enlarged and each with 2 or 3, 

 abnormally as many as 5, prominent, sharp spines; inferomarginals 

 with proximally 6 to 8 unequal, tapering, sharp, roughened, or 

 thorny spines, becoming reduced to 4 at middle of series, then 3, 

 and finally to 1 or 2 at end ; actinal intermediate plates usually with 

 a sharp thorny spine, at the base of which is a small blunt spatulate 

 pedicellaria with 2 swollen jaws; adambulacral plates with 12 to 17 

 small compressed furrow spines in a close comb, and 2 or 3 sharp, 

 heavy, roughened, subambulacral spines in an oblique series. 



Desci'iption. — Abactinal plates roundish, broadly elliptical, or sub- 

 hexagonal, those without spines smooth, slightly convex, and bor- 

 dered by small flattish granules with a convex or subtruncate margin, 

 the base being obscured by a very thin membrane. The central plate, 

 the primary radials and basals (except one) and upward of 8 other 

 median radial plates bear, on a convexity, an upright, tapering, sharp, 

 heavy spine, the longest (on the primary radials and central plate) 



