ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISITEK. 137 



NEARCHASTER VARIABILIS (Fisber). 



PI. 24, fig. 2; pi. 27, fig. 4; pi. 55, figs. 2, 2a; pi. 56, fig. 4; pi. 119, fig. 1. 

 Acanlharchastcr lariahilk Fisher, Zool. Anz., vol. 35, March 29, 1910, p. 550. 



Diagnoms. — Resembles N. aciculosus, but differs in having a fii-mer abactinal 

 integument, with closer-fitting plates; in the reduction of the spinules surrounding 

 abactinal primary spines, these being either very short, or, when lengthened, 

 comparativey few and and not forming a dense chevaux-dc-frise ; in having short 

 accessory marginal spinules; in having, as a rule, proximally four to six (instead of 

 one to three) furrow spinules; and in the variable extent of papular area on ray 

 (one-third to three-fifths length of ray). As this species is a close relative of 

 aciculosus, the description will be more intelligible if in the form of a comparison. 



Description. — The spines are usually stouter than in typical aciculosu.s. The 

 accessory abactinal spinules, which form such a characteristic armament in acicii- 

 losus, are here reduced greatly in length, in extreme cases forming a ring of insig- 

 nificant spinolets about the bases of the primary spines and a small paxilliform 

 group on the secoiulary plates. Sometimes a few, or rarely nearh' all, arc length- 

 ened on part of the primary jilates, but never on all, nor on the secondary plates 

 except very imequally and rarely. The papuhe are distributed all over disk except 

 for a narrow median interradial line, and extend along the ray a variable distance, 

 ranging from the ninth to the twenty-third superoiuarginal, or for about one-third 

 to three-fifths the total length measured along the side. Distally the papuUc are 

 confined to a rather naiTOW band on either side of the median radial area, and near 

 the tip of these bands the papulae are often few and rather widely scattered. Abac- 

 tinal pectinate pedicellariic very few or absent. The armature of the marginal 

 plates follows the reduction seen on the abactinal plates. The accessory spinules 

 are small and weak and clustered about the base of the three primary spines. Some 

 of the latter on inferomarginal plates may have flattened tips. Odd interradial 

 supcronuirginals three to five, more often four or five than three. Interradial 

 inferomarginals usually fall one behind the superomarginals. 



Adambulacral furrow spines proximally three to six, distally three to five, 

 slender, blunt, the two, three, or four central spines of the series the longest, and 

 proximally longer than width of plate. In the type there are five or six furrow 

 spines proximally, of wliich the tlu'ce or four centralmost are the longest. In 

 specimens from station 3330 there may be three, four, or five furrow spines, some- 

 what shorter than in tj'pe. Subambulacral spines, two, sometimes three, or very 

 rarely four on the first few plates, long, slender, blunt, in a diagonal transverse 

 series, the longer, blunter outer spine being on the adoral side of the plate. The 

 outer spine is about three times as long as width of i)late, or proximally two and 

 one-third to two and one-half times as long as longest furrow sjiine; the inner slightly 

 shorter. An aberrant specimen from station 3330 has oidj' one subambulacral on 

 most of the distal adambulacral plates. Along adoral border of i)late are a few very 

 small spinelets. There are eleven to thirt^m nuirginal sjunes on mouth plates, of 

 which the two inner are abruptly longer; five to seven long spines stand on the 

 actinal surface, forming a triangular group. 



