308 BULLETIN OF THE BUREAU OF FISHERIES. 



pointed granules, much shorter than the peripheral spinelets; ornamentation of the other paxillse 

 differing only in having less spinelets ami granules. At the tip of the ray the plates lose their tabulate 

 character. Many of the paxillse bear on the edge or nearer the center, a small upright pedicellaria, 

 whose 2 jaws are slightly higher than wide and very much larger than the central granules. Papulae 

 are numerous, single, especially conspicuous on radial areas because the paxillse are spaced. They are 

 absent from the very tip of the rays and a small interradial triangular area adjacent to the median 

 marginal plates. 



Marginal plates rather smaller than in any other speeies of the genus, and throughout most of the 

 ray the superomarginals are confined to the side wall; 30 in number from median interradial line to 

 extremity of ray, thin, slightly longer than high throughout most of ray, and forming a slightly arched, 

 steep bevel to side of body; first plate conspicuously higher, or wider, than long, and longer on inner 

 than lower edge. General surface covered with evenly spaced thimble-shaped granules which increase 

 in size toward the center of each plate, the peripheral being rather small and pinched. A few plates 

 bear pedicellaria' similar to those of the paxillse. Inferomarginals beyond the second plate alternating 

 with superomarginals and wider than high, forming a narrow border to the actinal area, thin, slightly 

 longer than broad, and the upper edge angular, like the lower edge of the superomarginals; granula- 

 tion rather coarser than that of superomarginals, square or prismatic, and very few pedicellarise on the 

 series. 



Adambulacral plates rather regularly quadrate and remarkable for the long furrow spinelets, of 

 which there are 5 in each series, strongly compressed, regular, round-tipped, theadoral slightly shorter 

 than the other 4, these spinelets reaching nearly across the furrow and tapering slightly as regards 

 their thickness, the tip being often beveled; on the actinal surface a longitudinal series of 3 spinelets, 

 the central longest ami about f the length of the furrow spinelets, the series standing midway between 

 furrow margin and outer margin, upon which are 3 or 4 less regular granules similar to those of the 

 actinal intermediate plates; lirst plate and a few others with a peculiar pedicellaria on actinal surface 

 consisting of 2 or 3 slender upright strap-shaped jaws, occasionally faintly spatulate, nearly as high as 

 the inner actinal series. 



Mouth plates slightly convex actinally and the furrow armature consisting of 8 spinelets, similar 

 in character to those of the adambulacral plates; the 2 inner larger than the others, ami those between 

 inner and outer members of the series slightly shorter, or, in other words, graduated in size from the 

 middle toward either end of the series; on actinal surface a number of elongate granules, and one of 

 the peculiar pedicellaria', the latter situated near the median suture at about middle of plate. 



Actinal interradial areas large, the plates extending to ninth inferomarginal or about half the 

 length of ray, arranged quite regularly in series parallel to the furrow, slightly convex and armed with 

 6-8 spaced, elongate, prismatic granules, usually forming an ornate rosette. 



Madreporic body convex, oval, situated nearer center than midway to margin; striations coarse, 

 undulating, interrupted, centrifugal. 



Locality: Station 4427, off Santa Cruz Island, Cal., 376 to 510 fms., black mud, broken stone.-. 



This species is remarkable for the small marginal plates, the high, slender, pedicellariae of the 

 actinal surface, and for the unusually long furrow spinelets. The peripheral spinelets of the abactinal 

 paxillse are also more elongate than is usual in the genus. Mediasler tenellus is therefore far removed 

 from sequalis, the type of the genus, and probably deserves to be set apart in a different subgenus, for 

 which the name Isaster of Verril] might prove available. The present form approaches the genus 

 Nymphaster in the actinal pedicellarise, hut does not have the marginal plates of that genus, and the 

 abactinal plating ami pedicellarise are not those of Nymphaster. Tun/Ins, however, must be regarded 

 as an aberrant member of Mediasler, probably nearer Nymphaster than any of the other species. 



Subfamily III1TASTKRIIX.E Verril], 1899. 



Genus HIPPASTERIA Gray. 



Hippasteria Cray. Ann. N. II.. VI, 1840, 279 i // - uropsea Gray - //. pkrygiana Pareliua). 



<> Marginal plates well developed, subquadrate, not separated by encroaching abactinal or actinal intermediate plates; 

 granules fairly or unite smooth. 

 /,, Pedicellarise shorter and higher. Dorsal surface very spiny; as a rule no pedicellaria- on marginal plates; actinal 

 pedicellaria- with oblong or subquadrate jaws; actinal intermediate plates not conspicuously tuberculate. 

 phrygiana 



