222 BUJULETIN "6, UNITED STATES NATIONAL, MUSEUM. 



Remarks.— Cladaster is a puzzling genus. Abactinally it reminds one strongly 

 of some form allied to Tosia, as it has no prominent spines nor any intermediate 

 secondary plates. But the prominent adambulacral spines are strikingly similar 

 to those of Hippasteria. There are, however, no promment marginal tubercles nor 

 bivalved pedicellarite, so that the similarity is not maintained to the ambitus. 

 CladaMcr seems to be unmistakably allied to the IIippasteriina3^ but it lacks what 

 are believed to be important characteristics of that group, the secondary abactmal 

 plates and the tuberculate or spiny marginals. 



CLADASTER VAXmUS Tlaher. 

 PI. 41, figs. 1, 2. 

 Cladaster validus Fisher, Zool. Anz., vol. 35, March 29, 1910, p. 552. 



Diagnosis. — R=17 mm.; r=10 mm.; R = 1.7 r. Arcuately pentagonal with 

 shghtly convex abactinal surface; broad marginals -with tumid naked abactinal sur- 

 face; regular abactmal plates bearing spaced, deciduous obovoid granules and spatu- 

 late pedicellariaj of small size; mth two furrow spines and one larger, heavier clavate 

 subambulacral spine; with unequal actinal intermediate granules, and relatively 

 large broadly spatulate pedicellarise. 



Description. — Abactinal plates regularly arranged in series parallel to the 

 medioradial, wliich fails to attain the terminal plate by the mdth of two supero- 

 marginals; from exterior the abactinal plates appear polygonal with rounded 

 corners, or roundish. Papulae single, six about each plate (or five interradially), 

 absent only from a small interradiiU area adjacent to margin. Covering of plates, 

 relatively large obovoid or ovoid well-spaced granules, usually one or two in center 

 and six, eight, or more on periphery; some of the larger plates in center of disk 

 have four to seven central granules. Scattered over abactmal surface are about 

 seventeen two-jawed broadly spatulate pedicellarise which have no depressions into 

 which they fit when open. The jaws are one and a half to twice as high as 

 granules, and have curved ends. 



Superomarginals six (or twelve to a side), and subequal except the last, which 

 is very small. They encroach on abactinal area conspicuously, ha\ang there a 

 quadrate contour, the proximal ones being nearer square than the distal; abactinal 

 surface of plates tumid and bare, except for a marginal series of spaced granules 

 similar to those of adjacent abactinal plates. Lateral surface of plates is covered 

 with spaced granules similar to latter but much larger. 



Inferomarginals seven (or fourteen to side) and similar to superomarginals, 

 except that the actinal surface has a small and less regular bare space. The inner 

 edge of the plates has two rows of granules, where the superomarginals have one, 

 and these are much smaller than granules of lateral surface of plates, the latter 

 being just like the superomarginal granules. Terminal plate tumid and almost 

 globose; naked above, but granular on the distal face. 



Actinal intermediate plates with coarse unequal granules, those on the outer 

 or marginal edge being larger than those on the side toward furrow or mouth angle. 

 Center of many of the plates bears a conspicuous tw-o-jawed broadly spatulate 

 pedicellaria, similar to but much larger than the abactinal, or in lieu of tliis occa- 

 sionally a granule. The plates without pedicellarise are, however, smaller, and 



