ASTEBOIDEA OF XORTH PACIFIC AND ADJACENT WATERS FISHER. 29 



I am unable to find a sing;le constant difference. The photographic fifjuros of 

 walthani are just hke ienebrarius. There are far greater differences between the 

 extremes of Alaskan specimens than between tj'pical teneirarius and walthani. 

 Consequently I believe the latter to be a synonym of the former. 



EREMICASTER PACIFICUS (Ludwlg). 



PI. 2, figs. 1-3. 



Porcellanaster pacijicus LuDwio, Mem. Mus. Comp. Zool., vol. 32, 1905, p. 89, pi. 6, figs. 28, 29; 



Zool. Anz., vol. 31, 1907, pp. 317, 318. 

 Eremicasler pacijicus Fisher, Zool. Anz., vol. 32, 1907, p. 14. 



Diagnosis. — Rays five. R = 21 mm.; r=10 mm.; R = 2.1 r. Breadth of ray 

 at interradial line, 11 mm.; at outer end of lateral cribriform organ, 6. .5 mm.; length 

 of abactinal peduncle, 5 to 7 mm. Disk rather large and rays of median length; 

 interbrachial arcs well rounded. Cribriform organs three; no segmental pits or 

 papillae; adambulacral plates with tw^o sharp spinelets; marginal plates eight or 

 nine, the superomarginals with one, rarely two, upright spinules; abactinal surface 

 W'ith spaced spinelets extending to outer cribriform organ; actinal intermediate 

 areas with spaced spmeltts. 



Description. — Abactinal membrane capable of inflation. Disk and basal part 

 of raj', as far as outer edge of lateral cribriform organ covered with spaced deli- 

 cate, terete spinelets, each invested in a thin membrane. In one specimen tlie spine- 

 lets extend a short distance beyond cribriform organ. They are about 0.5 mm. 

 high and spring from sunple subcircular perforated plates embedded in the abactinal 

 membrane. As a rule these plates have an irregidar outline and are about one-half 

 to two-thirds as broad as height of spinelet. The plates are more or less spaced 

 and irregularly between them emerge the papulae, singly. They have the appear- 

 ance of being about as numerous as the spmelets. The central prolongation of the 

 integiunent or peduncle contains crowded plates with rudimentary spinelets as in 

 tenebrarlus, and no papuhp. In the integument of ray beyond the lunit of spmelets 

 are simple subcircular perforated plates usually uneven or more or less toothed on 

 margin; occasionally smooth. The plates are somewhat larger than those of disk, 

 the largest being 0.6 mm. in diameter, a small one about 0.3 mm.; whereas on the 

 spiniferous area at base of ray the largest are 0.35 to 0.4 mm., and are thicker in the 

 center. The abactinal area varies in width on ray, even in same specimen, according 

 as marginal plates are arched inward. Occasionally two or three isolated spinelets 

 occur on outer part of ray. 



Marginal plates in form about as in E. tenebrarius. Superomarginals eight or 

 nin e, each with an upright glassy tipped spinule on upper edge of plate, these about 

 as high as plate when perfect and tlecreasing m size toward end of ray. Occasion- 

 ally a second shorter spinule is present. Inferomarginals the same in number as 

 superomarginals, confined to siile wall of ray and longer than liigh. 



Terminal plate fairly large, deeply concave toward abactinal area. There is 

 one temiinal spinule, and below at either side of end of furrow, one; behind termi- 

 nal spinule on abactinal edge of plate a row of two to five spinelets on either side. 

 In a small specinuMi from station 2859 these are lacking. 



