ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 89 



connecting ossicles) bearing, along with the marginals, a slender acicular spine incased 

 in a retractile, distally expanded sheath beset with a terminal wreath of very numerous 

 crossed pedicellariae; inferomarginal plates spaced; superomarginal plates just above 

 inferomarginals and connected with them, but alternate superomarginals abortive 

 except at very base of ray; ambulacral plates not so crowded as in Asteriinae, and 

 about the same as in Coronaster, the ambulacral pores, in fully grown specimens, 

 being in two slightly zigzag series, except at ends of the ray where the line is straight; 

 tube-feet in four ranks except at base of ray (two ranked in young specimens) ; adam- 

 bulacral plates short and crowded as in Coronaster, monacanthid; oral plates of 

 Pedicellaster type, but more compressed; interbrachial septa small, entirely mem- 

 branous; no Polian vesicles; ampullae single; tube-feet long, with sucking disks; 

 gonads two to each ray, attached at the side about on a level with the superomarginal 

 plates; intestinal coecum entire; crossed pedicellariae with two enlarged terminal 

 teeth to each jaw; straight pedicellariae not unguiculate nor broadened terminally; 

 disk circular, rays rather deciduous, 12 to 20, but undoubtedly fewer in very young 

 specimens; body wall thin; papulae in groups of 2 or3 to 15, rather long and vermiform, 

 numerous, arranged on ray in poorly marked longitudinal series; two or three to five 

 papulae spring from a single pore. 



Remarks. — This well-marked genus, which was named for the late Dr. Richard 

 Rathbun, I compared originally with Pycnopodia Stimpson, to which it bears a 

 resemblance entirely superficial. Rathbunaster seems to be more closely related to 

 Coronaster than to any other known genus; and next to Coronaster, Labidiaster Liitken 

 appears to be its nearest relative. 



Both Coronaster and Labidiaster have a wide meshed reticulate skeleton made 

 up of slender, lobed, cruciform plates, arranged in longitudinal and transverse series, 

 and either joined directly by their lobes, or by one or two slender, imbricating inter- 

 mediate ossicles. The papular areas are very large and usually fairly regularly 

 quadrate except dorsolaterally on the basal portion of the ray where the more or less 

 irregular dorsolateral (or adradial) series of plates introduces some irregularity. In 

 neither genera are there actinal plates. The dorsal and lateral walls of the ray are 

 composed of the two series of marginals, the adradials (proximally only) and the 

 carinals. In both genera, but particularly in Coronaster, we have the characteristic 

 sheathed and wreathed acicular spines. In both genera the abactinal skeleton, and 

 to a certain extent the marginal connecting ossicles tend to disappear on the outer 

 part of the ray. In Rathbunaster the abactinal and marginal connectives, a part of 

 the abactinal primary plates and about half of the superomarginal plates have 

 disappeared. 



RATHBUNASTER CAMFORNICUS Fisher 



Plate 12, figs. 5, 6; Plates 39, 40, 41 



Rathbunaster californicus Fisheb, Proc. Wash. Acad. Sci., vol. 8, Aug. 14, 1906, p. 137; Bull. 



U. S. Nat. Mus. 100, vol. 3, 1919, p. 493— Verkill, Shallow-water Starfishes, 1914, 



p. 197. 



Diagnosis. — Rays usually 17 (varying from 12 to 20). R 155 mm. (variable), 



r23 mm.; R = 6.7 r (variable) ; breadth of ray at base, 9 to 11 mm. Disk nearly Hat. 



circular; rays long, slender, more or less constricted at base, adjacent to disk, and 



somewhat inflated proximally; abactinal integument thin, membranous; abactinal 



