ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER. 101 



Genus DYTASTER Sladen. 



Dytaster Sladen, Narr. Challenger Exp., vol. 1, 1885, p. 608; Challenger Asteroidea, 1889, p. GO. 



Type," D. nobilis Sladen. 

 Crenasterb Perkier (not d'Orbigny), Annales dessci. nat., 1885, p. 71; Exp^-d. Bci.du Travailleiir 



etdu Talisman, 1894, p. 306. 



Diagnosis. — Di.sk rather small; rays very long and attenuate often subcarinate 

 along the median line abaetinally, very shghtly flexible. Marginal plates rectangular; 

 the superomarginals thin and lamelliform, confined more or less to the lateral wall 

 of the ray, which is usually vertical. Plates of upper series directly superposed on 

 the corresponding plate of the inferior series, and the contingent horizontal margins 

 of both plates are consecjuently straight. Plates of both series usuallj' armed with 

 one more or less prominent thorn-Uke spine, but this may be aborted or may be 

 absent, especially in j'oung forms. The general surface of the plates of both series 

 covered with short papilliform spinelets or granules. Abactinal area with small 

 rounded scale-like plates bearing small jjaxilla; more or less well developed; no 

 definite order of arrangement. Papula; numerous or not, generallj^ distributed (?) 

 or absent from outer half of raj'. Actinal interradial areas fairly well developed, 

 vnth numerous intermediate plates arranged in more or less definite colunms. 

 Armature of adambulacral plates consisting of a longitudinal furrow series of short 

 spines standing parallel to one another and one or more longitudinal series of 

 papilliform s])inelets or granules on the actinal surface; in some forms the first 

 series are well-developed spinelets and nearly as large as those of furrow series; and 

 in some there is a single enlarged spinclet among the first series. Madreporic body 

 ver3' large, compound, placed near the marginal plates and covered with numerous 

 paxillte. Pedicellarise (sid)valvular) may be present on the abactinal and actinal 

 interradial areas. Anus present, subcentral. Actinostome and ambulacral furrows 

 wide; tube feet pointed. Gonads (alwaj's?) extending, in numerous dichotomously 

 branched tufts, fur along ray in a series parallel with marginal plates. 



DYTASTER GILBERTI Fisher. 



PI. 17, figs. 1-3; pi. 53, figs. 3, 3a. 

 Dytaster gilbirli Fisher, Bull. Bur. Fisheries for 1904, vol. 24, p. .300, June 10, 1905. 

 Diagnosis. — Related to D. exilis Sladen. Rays five. R = 114 mm.; r = 22 

 mm.; R = 5.2 r. Breadth of ray at base 22 mm.; at tenth superomarginal, one- 

 fourth length of ray, 17.5 mm. Rays elongate, robust, tapering at first very 

 slightly, then more rapidlj', to a pointed, attenuate, extremity; abactinal integu- 

 ment inflated on disk, plane on rays; lateral wall of ray vertical on proximal half, 



"No type was mentioned by Sladen in hie original description of the genus in the Narrative, but 

 he fortunately mentions that ''at the same station (No. 325) was dredged the genus Dytaster." The only 

 Dytaster taken at that station was D. nobilis, upon which he evidently based the generic diagnosis. 

 The genus should date from 1889. 



6 This name has no status in nomenclature, irrespective of the status of the group to which it has been 

 applied. Crenastcr has been employed previously in zoology by d'Orbigny. (Prodrome de pal^n- 

 tologie, vol. 1, 1850, p. 340.) 



