ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 113 



and a fairly regular dorsolateral on either side, though the latter is frequently either 

 absent or represented by an incomplete series of much smaller spines than the carinals. 

 Normally every alternate carinal plate carries a robust, terete, slightly tapering, or 

 sometimes faintly capitate, blunt or truncate, terminally roughened spine, there 

 being 20 to 24 such in medium and large specimens, the proximal, 2 to 2.5 mm. long 

 (type). In the type a very few plates carry two to four such spines. Dorsolateral 

 spines vary from a nearly complete series in the type to entire absence. The majority 

 of specimens have only a few small spines distributed at irregular intervals along the 

 proximal half of the ray. A pentagon of spines on the disk surrounds a prominent 

 central spine, or group of two or three. 



Superomarginal spines, 15 to 22 in medium-sized and large specimens, occur on 

 alternate plates and are generally closely similar to the carinals but a little longer. 

 They vary from a slight to a decided taper, are bluntly pointed, round-tipped, or 

 truncate, and in the type are frequently compressed and gouge-shaped at the end. 

 In small specimens the superomarginals may be slightly shorter than the carinals. 



Intermarginal channel relatively broad, especially in small and medium-sized 

 specimens, where it is as broad as the dorsolateral area (but in the type only about 

 0.5 or 0.6 as broad). Inferomarginal spines two to each plate, in an oblique transverse 

 series, on the actinolateral border of the ray, along which they form a bristling fringe. 

 The spines are a little shorter than the superomarginals, are slightly tapered, and the 

 outer has a flattened truncate tip. The inner is a trifle slenderer, may be similar in 

 form or nearly terete and bluntly pointed. Under especially favorable conditions 

 the thin web connecting the bases of the outer spines may be seen. In a specimen 

 from station 3110 it involves about half the length of the spines. The inner spine is 

 independent of this lateral web but is more or less bound to the outer spine by a 

 membrane at the base. The lateral web is homologous with the ordinary sheath of 

 the dorsal spines, and like it is usually very strongly contracted in alcoholic specimens. 



Actinal channel very narrow. A single series of actinal plates, which in the 

 type extends far along the ray, is wedged between the inferomarginal and adambu- 

 lacral series — one plate to each inferomarginal. In the type and a few of the medium- 

 sized specimens the plates bear a single, terete, tapering, blunt spine for about half 

 the length of the ray. There is a good deal of variability in respect to the numbers 

 of actinal spines. In a specimen from station 3110, with R 50 mm., the plates are 

 small and the spines entirely absent. In three specimens from station 4431: One, 

 with R 37 mm., has spinelets on the first five or six plates (17 plates in the series); 

 another, with R 46 mm., has only one or two or no spine to each series; a third, 

 with R 58 mm., has 13 or 14 spines, the series reaching halfway to tip of the ray. 

 Neither the inner marginal nor the actinal spines carry any pedicellariae. 



Adambulacral spines two, slender, tapering, bluntly pointed and nearly equal. 

 There are 38 adambulacral plates in the length of 10 inferomarginals a< base of ray. 



Oral angle, broader than in Orthasterias, composed of mouth plates and two pairs 

 of contiguous adambulacral plates. In small specimens there is but one pair of con- 

 tiguous adambulacrals. Each pair of mouth plates has a fan of four spines on the 

 actinostomial margin, the median two long, flattened, narrowly lanceolate to sub- 

 spatulate, the laterals only about one-third to one-half as long. There is usually 

 but one suboral to each mouth plate (occasionally three to the pair of plates) and 

 these as well as the first few adambulacral spines are sometimes markedly spatulate 



