ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 25 



8TNOP3IS 0? SPECIES OP FEEYELLA HEREIN DESCRIBED 



a 1 . Plates of genital region smaller (20 to 30 in a line across ray at widest part) and very numerous; 

 spinelets very small in small groups; one aboral furrow spinelet; proximal subambulacral 

 spine terete with a slightly capitate truncate tip; tliree actinostomial oral spinelets; pedi- 

 cellariae all minute microplax. 



a 2 . Plates of genital region large (8 to 12 in a line across ray at widest part) and fewer; spinelets 

 larger; one or two aboral furrow spinelets; proximal subambulacral spines spatulate, with 

 2 to 4 pronged tip, or with prongs only; two actinostomial oral spinelets; pedicellariae 

 of adambulacral, oral, and abactinal spinelets large insignis. 



FEEYELLA M1CROPLAX iFlaher) 



Plate 4, Figures 1, la-1/; Plate 7, Figure 1; Plate 10; Plate 12, Figure 4 



Freyellidea microplax Fisher, Ann. and Mag. Nat. Hist., ser 8, vol. 20, 1917, p. 430. 

 Freyella microplax Fisher, Bull. U. S. Nat. Mus. 100, vol. 3, 1919, p. 538. 



Diagnosis. — Rays 12, not deciduous, only moderately long, with a short swollen 

 genital region about 4 r in length. Disk closely covered with short spinelets, four 

 or five to a plate; genital region of ray covered with small transversely oriented, 

 elliptical, somewhat irregular plates bearing groups of two to eight small spinelets; 

 19 or 20 plates can be counted across ray at widest part. Short lateral spine opposite 

 alternate adambulacral plates. Adambulacral armature, one aboral furrow spinelet, 

 and one subambulacral spine, with truncate enlarged tip at base of ray; first adam- 

 bulacral plates of adjacent rays not fused, the outer end of mouth plates intervening; 

 oral armature: three actinostomial spinelets and one short, sharp, suboral spine. 

 R 170+ mm., r 10 mm., R = 17+ r; thickness of disk, 4 mm.; width of ray at base, 

 4.5 mm.; breadth of actinostome, 13 mm. 



Description. — The top of the disk is flat and only slightly elevated above the 

 rays, which slope gradually into the disk without a break, or shoulder. The disk is 

 thickly covered with terete blunt spinelets usually four or five to each plate. The 

 spinelets are sheathed in membrane which gives them their characteristic blunt form, 

 the calcareous portion being very sharp. Certain scattered plates have only two or 

 three spinelets. The spinelets are about 0.5 mm. long and those of each plate tend 

 to radiate apart slightly, the separate groups being usually less than 0.5 mm. apart. 

 There are a few larger plates observable in favorable specimens which have 15 to 20 

 spinelets. These are probably primary apical plates. At the base of the spinelets 

 are one to several very minute inconspicuous pedicellariae. 



The genital region is conspicuously inflated, short, and thickly covered with very 

 numerous transversely oriented groups of about five (two or three to five, less com- 

 monly, six, seven, and eight) delicate, skin-covered, blunt spinelets (very sharp when 

 dried) borne on elliptical transversely oriented plates which usually are slightly 

 spaced when the ray is swollen to its maximum. When the ray is only slightly 

 swollen, the plates touch, especially in the mid-dorsal region. Minute, inconspicuous 

 pedicellariae are present on the basal portion of the spinelets. The spaces between 

 the groups of spinelets are small, usually about one-half the width of the group of 

 spinelets in undried specimens. Beyond the region of plates (which is about twice 

 the diameter of disk from base of ray) there are broad bands of pedicellariae, the alter- 

 nate ones usually much interrupted. The spaces between the bands are less than the 

 width of the band itself. 



