154 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



lateral, diplacanthid inferomarginals by a broad descending lobe, with intervening 

 papular areas; each inferomarginal spine with its own sheath capped by several 

 clusters of crossed pedicellariae; no actinal plates nor actinal papulae; adambulacral 

 plates small and crowded, monacanthid, with pedunculate furrow bouquets of small 

 straight pedicellariae; large ovoid pedunculate straight pedicellariae; crossed pedicel- 

 lariae with a very conspicuous enlarged lateral tooth on outer side of terminal lip and 

 numerous shank teeth; madreporic body single, tube-feet very numerous, large, 

 crowded, forming six or eight longiseries in large specimens; ambulacral plates, 

 thin, crowded; pores quadriserial (except near actinostome) ; adoral carina long, 

 narrow; mouth plates compressed, small; actinostome large; stomach eversible; 

 gonads opening abactinally. 



Remarlcs. — This genus is peculiar to the west coast of North America and con- 

 tains one species which ranges from Unalaska to San Diego, Calif. Its only close rela- 

 tive is Lysastrosoma, of Hokkaido and the Gulf of Tartary, from which it differs in 

 having numerous rays and directly imbricated marginal plates. 



In Lysastrosoma there are five rays and broad mouth plates. In Pycnopodia the 

 very young at first have six rays (exceptionally five). Usually but not invariably 

 new rays are interpolated in pans on either side of an axis of symmetry passing along 

 a definite radius, which is the second, clockwise, from the madreporic interradius of 

 normal six-rayed young. 



PYCNOPODIA HELIANTHOIDES (Brandt) 



Plates 77-80 



Asterias helianthoides Brandt, Prodromus, 1835, p. 271. (Sitka).— Stimpson, Boston 

 Journ. Nat, Hist., vol. 4., 1857, p. 529. 



Pycnopodia helianthoides Stimpson, Proc. Boston Soc. Nat. Hist., vol. 8, 1861, p. 261.— A. 

 Agassiz, North American Starfishes, Mem. Mus. Comp. Zool., vol. 5, no. 1, 1877, p. 100, 

 pi. 13 (structure). — Whiteaves, Trans. Royal Soc. Canada, vol. 4, 18S6, p. 116. — Ritter 

 and Crocker, Proc. Wash. Acad. Sci., vol. 2, 1900, pp. 247-274, pis. 13, 14.— Clark, 

 Proc. Boston Soc. Nat. Hist., vol. 29, 1901, p. 329 (Port Townsend).— Verrill, Shallow- 

 water Starfishes, 1914, p. 198, pi. 29, fig. 1; pi. 30; pi. 31, figs. 1, 2; pi. 73, fig. 1; pi. 

 74, figs. l-3a; pi. SS, figs. 7-7<i (7c very inaccurate); text-fig. 2, p. 35 (very inaccurate; 

 misleading). — Hamilton, W. F., Journ. Comp. Psychology, vol. 1, 1921, p. 475 (be- 

 havior) . 



Diagnosis. — Disk large; rays upward of 24, usually 15 to 23 in adult specimens, 

 capable of inflation, gently tapered, very soft and flexible in live specimens owing to 

 absence of a connected dorsal skeleton; whole surface of body crowded with large 

 clumps of prominent papulae among which are scattered thick pompons of crossed 

 pedicellariae, surrounding usually a slender, sharp, or blunt spine; marginals heavily 

 stoled, and somewhat larger than the scattered dorsals, the superomarginals lateral, 

 the inferomarginals (two to a plate) actinolateral or actinal in position; adambula- 

 crals sunken below level of inferomarginals, slender, in single longiseries; furrow 

 broad, tube-feet large; usually numerous large ovoid ped uncled dermal pedicellariae; 

 skin tough, soft, highly glandular, completely obscuring skeleton. R upward of 400 

 mm.; commonly 200 to 300 mm. 11 = 2.5 to 3 r. (Specimens shrink considerably 

 in preservation due to the highly muscular integument.) 



Description. — Abactrnal surface very soft and yielding, having very numerous, 

 irregularly and closely placed clumps of large, slender, numerous crowded papulae. 

 In large specimens there are upward of 75 papulae to the larger groups and 30 to 50 

 in the medium-sized. Spaced among the clusters are convex, circular, bouquets of 

 very numerous crowded crossed pedicellariae, borne on sheaths having on the outer 



