ASTEBOIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 25 



Eremicaster tcnebrariug Ludwig, Zool. Anz., vol. 31, 1907, p. 318. — Fisher, Zool. Anz., vol. 32, 



1907, p. 14. 

 Eremicaster waltharii Ludwig, Zool. Anz., vol. 31, 1907, p. 318. 



Diagnosis.— Rays five. R = 38 mm.; r = ll mm.; R = 3.45 r. Another .speci- 

 men: R = 42 mm., r = 9 mm., R = 4.0G r. Breadth of ray at interradial line, 14 to 15 

 mm.; at outer edge of lateral cribriform organ, 9 mm.; height of "epiproctal cone,'' 

 3 to 5 mm. in different specimens. Related to £". cro^sws (Sladen). Rays elongated, 

 stout fairly slender, abniptly tapering at base, but only very gradually on outer 

 three-fourths; ambulacral furrows very wide. Superomarginals t3q)ically with 

 one or two sy)inules on upper edge; inferomarginals unarmed, as many as nineteen 

 in number; terminal plate with three to six spinelets; adambulacral plates with 

 one or two spinelets (usually two in large examples), and one segmental pa])il]a 

 which is transformed into a spinelet distally on ray; mouth plates with two seg- 

 mental papillie, with one unpaired spme at inner angle and with one smaller spinelet 

 at either side. Actinal interradial areas smooth; intermediate plates extending 

 to fourth or fifth inferomarginal. Spinelets on abactinal membrane extending 

 as far on ray as lateral cribriform organ; spinelets membrane-covered, terete, and 

 spaced; abactinal area on ray very narrow. 



Description. — The abactinal area is slightly sunken below level of the uj)per 

 edge of superomarginal plates, and is narrow on rays; but it varies in width according 

 as the marginal plates are arched inward. On outer two-thirds of ray it is often 

 reduced to a mere line and is never wider than a neighboring superomarginal. 

 Abactinal integument is thin but resistant, and on disk and basal portion of ra}- 

 (as far as outer cribriform organ) is covered with simple, slender, spaced spinelets, 

 which are sheathed in membrane so that they appear terete and tnincate. They 

 are sHghtly longer toward edge of disk. Beyond the outer cribriform organ no 

 'spinelets are present in the abactmal integument. On the central prolongation 

 of the integument, or "epiproctal" cone, which is from 3 to 5 mm., the spinelets 

 are minute, and when seen in connection with their simple, perforated, "embiy- 

 onic" plates greatly resemble "tables," such as are present in the skin of many 

 holothurians, the spinelet representing the spire. The abactinal plates are scattered 

 on the ray, are closer on the disk, and crowded on the central prolongation or 

 peduncle. They are, in form, small circular perforateil plates, with a smooth or 

 irregular contour, and do not dift'er material!}' from the perforated plates of many 

 -holothurians. Scattered among the spinelets (but not elsewhere) are numerous 

 papulfe, especially in the interradial areas. The}' a])pear to be absent from the 

 epiproctal cone. 



The marginal plates always arch inward more or less so that when vi(>weil 

 from above the contour of body is usually defined by inferomarginals. Supero- 

 marginals (eighteen or nineteen in large specimens) are nearly quadrate and are 

 larger than corresponding inferomarginals. They decrease regularly in size distally. 

 Each plate bears, on its upper edge, one or two robust, tapering, sharp spinules, 

 these forming a row to terminal plate. These spinelets are sometimes nearly 

 as long as height of plate. A single spine stands at the top of the suture between 

 the median and eitlier lateral or cribriform organ. (For variations in presence 

 of superomarginal sj)ines, see Variations on p. 27.) 



