166 BULLETIN 76. UNITED STATES NATIONAL MUSEUM. 



genus is remarkable for the tliin dorsal integument, few papular pores, and numerous 

 (seven or eight) small furrow spinelets. The marginal plates are unusually small. 

 "Abactinal plates polygonal, flat, thin, closely united, finely granulated, with two 

 or more rows of granules around the edges, but wnth a small, central, round, naked 

 area, in the type. Papular pores rudimentary, few, small, obscure, not visible 

 except when the plates are denuded; they occur only between the three central rows 

 of plates, in a very circumscribed basal radial area. Actinal plates granulated, 

 rather large, angular, of various forms, not forming regular rows. A small elongated 

 pedicellaria, with two, three, or four spatulate blades, occurs on the center of many 

 of the adambulacral plates an<l on some of the actinal plates" (Verrill). 



TosiA Gray and Pextagonaster Gray. — The type of Tosia is T. australis Gray; 

 that of Pentagonaster, P. pulchellus; both montotypic when first characterized. 

 Stephanankr Ayres and Astrogonium Sladen are synonymous with Pentagonaster. 

 There are four specimens of the type species of Pentagonaster in the Museum of 

 Comparative Zoology. Stephanaster hourgetl is excluded from the genus and made 

 the type of a new genus, Spliseriodiscus. 



It seems necessary to segregate the Australian species in these two genera, as 

 they do not agree with European or American species commonly called Pentagonas- 

 ter and Tosia. The latter are now classed in several quite different groups — Ceram- 

 asfer, PUnthaster, Peltaster, Litonotaster, and SpJiseriodiscus. 



Pentagonaster differs from Goniaster in lacking abactinal tubercles; in having 

 the last marginal plate of both series enlarged; in lacking abactinal secondary 

 ossicles, and numerous papular pores separated by intermediate granules between 

 the dorsal plates of papular areas; in having abactinal and actinal intermediate 

 plates free of granules except for a marginal series of granules (applies to adults). 



Pentagonaster differs from Sphxriodiscus in having the last marginal plate of 

 both scries (not the penultimate) largest; in having the marginals entirely naked; in 

 lacking the flat granulated abactinal and actinal plates (these being more or less 

 convex and naked in Pentagonaster). 



Pentagonaster is distinguished from Tosia by the enlarged distal marginal of 

 both series (if a marginal is enlarged in Tosia it is the last superomarginal only) ; in 

 the character of the pedicellaria^ which have narrow spatulate jaws (as in Goniaster) ; 

 in Tosia they are low, bivalved and wider than high, or are absent altogether. 



In the type of Tosia, there are very few short bivalved pedicellarire on the 

 abactinal plates; the actinal surface lacks pedicellariie, but the plates are naked 

 centrally, there being usually two or even tliree or four rows of granules around 

 each plate. The adambulacral plates are very like those of Pentagonaster — wider 

 than long, with two furrow spinelets, thick and stubby, behind these two more, and 

 then two rows of about three Granules each. The abactinal plates are strongly 

 stellate not only on the radial but interradial areas as well. Single papulae emerge 

 between the lobes of plates, and are distributed all over the disk from center to 

 angles. 



The group to which T. tuberculafa (Gray) belongs is somewhat different— that is, if 

 the specimens in the Museum of Comparative Zoology are really Gray's species. The 

 abactinal plates are arranged in radial and parallel rows, but next to radial series in 

 a small specimen, and over most of the petaloid radial area in a larger specimen are 



