ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 29 



Genus ASTROCLES Fisher 



Astrocles Fisher, Ann. and Mag. Nat. Hist., ser. 8, vol. 20, 1917, pp. 426, 430. Type A. 

 actinodetus Fisher; Bull. U. S. Nat. Mus. 100, vol. 3, 1919, p. 504. 



Diagnosis. — Related to FreyeUa but plates of ray localized in transverse arches 

 separated by intervals without plates; plates flat, not forming prominent carinate 

 costae as in Brisinga; gonads two to each ray, opening each by a single aperture on 

 side of ray a little less than 1 r from the disk; furrow spinelet and proximal subambu- 

 lacral spines with expanded modified tips; in interbrachial angle first pair of adjacent 

 adambulacral plates joined only at proximal end, not for their whole length as in 

 typical FreyeUaster; no prominent pair of first marginal plates directly above the 

 first pair of adambulacrals; touching the lower end of the slender interradial plate 

 is a pair of small plates. These are the outer ends of the mouth plates which project 

 dorsally behind the proximal ends of the first pair of adambulacral plates, as in 

 FreyeUa. The adambulacral plates segregate this dorsal part of the mouth plates 

 from the actinal spine-bearing portion; first and second adambulacral plates as well 

 as the upper part of the second and third ambulacrals joined by a normal muscular 

 symphysis; no syzygy present. 



Remarks. — This curious genus agrees with FreyeUa in certain important features — 

 the absence of a proximal adambulacral syzygy, absence of marginal plates above 

 the first few adambulacral plates, and presence of only two gonads to each ray. 

 I think the independent abactinal skeletal arches of the ray have nothing to do with 

 those of Brisinga. The plates are flattish and resemble more nearly segregated 

 abactinal plates of FreyeUa than they do the slender compressed costal plates of 

 Brisinga and near allies. 



ASTROCLES ACTINODETUS Fisher 



Plate 4, Figures 3, 3a-3fe; Plate 5; Plate 11; Plate 12, Figure 2 

 Astrocles actinodetus Fisher, Ann. and Mag. Nat. Hist., ser. 8, vol. 20, 1917, p. 430. 



Diagnosis. — Rays 11, not very deciduous; disk fairly large, covered with circular 

 plates bearing one to three spinelets; genital region of ray 3.5 to 4 r in length, or about 

 one-sixth total length of ray, and crossed by 25 to 27 pretty regular transverse arches 

 of depressed elliptical, crenulate plates covered with a felting of minute pedicellariae 

 and bearing small spinelets in transverse series; intervals between arches without 

 plates or pedicellariae; lateral spine opposite alternate adambulacrals, very slender 

 and delicate; adambulacral armature consisting of one aboral furrow spinelet with 

 tip greatly broadened and subtriangular in form, and one subambulacral spine, those 

 on proximal half or two-thirds of genital region with an enlarged bifid tip; mouth plates 

 with three actinostomial spines, expanded flattened and more or less irregular in form, 

 one aboral, modified, furrow spinelet and one suboral pointed spine; in interbrachium 

 the first pair of adjacent adambulacral plates touch or join only at their proximal 

 ends— are not fused the whole extent of their interradial faces, nor is there directly 

 above them a prominent pair of first marginal plates as in Brisinga. 



Description. — The disk is only very slightly elevated above the level of the base 

 of rays, and the latter slopes upward to the disk without any abrupt shoulder. Sur- 

 face of disk fairly plane. Disk plates circular, slightly elevated at middle for artic- 

 64406—28 3 



