ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 149 



First pair of postoral adambulacral plates with the median or interradial suture much shorter than 

 that of the mouth plates; intermediate superomarginal ossicles very weak; lacking on outer 

 part of ray; submicroscopic perforated plates numerous in abactinal integument. 



anthosticla Fisher. 



First pair of postoral adambulacral plates with the median or interradial suture longer than that 

 of the mouth plates; intermediate superomarginal ossicles stout proximally, persisting to the 

 end of ray; submicroscopic perforated plates absent except at end of ray, where there are a few 

 laterally desmiora Clark. 



LYSASTROSOMA ANTHOST1CTA Fisher 



Plate 73, Figures 1, lo-lj; Plate 75 



Lysastrosoma anthosticta Fisher, Ann. and Mag. Nat. Hist., ser. 9, vol. 10, 1922, p. 591, 

 figs. 1 and 2; Proc. U. S. Nat. Mus., vol. 64, art. 3, 1924, p. 2, text figs. 1, 2, 3, 5, pis. 1, 2. 



Diagnosis. — Rays five. R 63 mm., r 9 mm., R = 7 r ; breadth of ray at base, 8 to 

 10 mm. Disk small; rays marked off from disk by a slight constriction at base; 

 abactinal surface more or less swollen; entire body very soft and flexible; axils rounded; 

 abactinal skeleton reduced to widely separated, isolated plates, interspersed with 

 minute spineless vestigial "holothurioid" platelets; abactinal surface with numerous 

 widely spaced, small, acicular spinelets mostly hidden by obconical tough sheaths 

 bearing numerous crossed pedicellariae on the distal expanded end; each alternate 

 superomarginal plate with asimilar but much larger spine (3 mm.) ; each inferomarginal 

 with two subequal spines in a single sheath bearing terminal pedicellariae; adambulac- 

 ral plates monacanthid; one pair of enlarged adambulacrals meeting behind the large 

 oral plates, their median suture shorter than that of oral plates; straight pedicellariae 

 very small, lanceolate; tube-feet large, crowded, in four rows, furrows broad. 



Description. — The whole body is very weak and flabby much as if it had been 

 decalcified. This is due to the absence of a connected abactinal skeleton and also to 

 the very loose connection between the marginal plates. Even the ambulacral and 

 adambulacral plates are rather loosely articulated and the plates themselves are not 

 hard and firm but rather spongy. 



The abactinal skeleton consists of widely separated, entirely disconnected, small 

 irregular or faintly lobed plates, ordinarily from 0.4 to 0.6 mm. in diameter, each 

 bearing a slender acicular spine surrounded by a thick tough sheath broadly expanded 

 at the summit, which is very thickly beset with crossed pedicellariae. These spine- 

 lets (1 to 1.5 mm. long) are conspicuously smaller than the superomarginals and are 

 not at all in regular series. There appears to be the equivalent of about five longi- 

 serics, although at the base of some rays the arrangement is far too irregular to admit 

 of exact determination. Scattered all over the abactinal surface among the spinif- 

 erous plates and completely immersed in the integument, are numerous perforated 

 "vestigial" plates of a generally subcircular or elliptic contour, which resemble 

 holothurian plates and are 0.08 to 0.18 mm. in diameter. (PI. 73, fig. le.) The skin 

 is rather thickly beset with small lanceolate straight pedicellariae of several sizes, the 

 number varying in different examples. 



Alternate superomarginal plates are spineless and smaller than the spiniferous. 

 While at the very base of the series they touch one another, over most of the ray they 

 are spaced, and are connected by a curious festoon of small intermediate ossicles as 

 indicated in figure 1. (PI. 73.) The alternate and larger subquadrate superonnu- 

 ginals carry a conspicuous acicular spine about 3 mm. long with a tough sheath ex- 

 panded and convex at the summit, which usually hides the tip of the spine and is 



