ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 73 



Description. — Paxilhc of abactinal surface small, not crowded except at center 

 of disk; arranged in transverse rows at sides of tlie paxillar area of rays; five or 

 six such series corresponding to two inferomarginals at base of the raj^s; no definite 

 arrangement along median radial line, nor in central portion of disk ; size of paxillse 

 decreasing toward extremity of rays, and on the disk, toward center; on the rays 

 the largest are along midradial line, and on disk about midway between center and 

 edge. Each paxilla consists of a compact, flat-topped, subcircular or irregularly 

 elliptical group of small, cjdindrical, round-tipped membrane-invested spinelets, of 

 which two, three, four, or five (on larger paxillw) are stouter and occupy the center 

 of tabulum, being closely surrounded by ten to fifteen slenderer spinelets, which 

 frequently have the membrane thinner. Small papulae are visible in the spaces 

 between the paxillae, especially on rays. 



The abactinal plates or bases of paxillae (viewed from inner or ccelomic surface 

 of abactinal integument) are generall}' circular in outline except on outer half of 

 ray, where they are longitudinally elliptical, and in center of disk and along mid- 

 radial line, where they are often slightlj^ irregular. The plates are spaced, and are 

 much closer together in center of disk and along median radial line, where there 

 are no papulse, than along sides of abactinal area. On the latter areas they are 

 arranged in very regular transverse rows which assume an interradial direction on 

 disk, and the plates increase in size toward the midradial line, where for a width of 

 about three plates there are no papulte and no regular arrangement of plates. The 

 plates decrease in size toward center of disk. The papulae are single and so arranged 

 that there are usually six about each plate of the papular areas. The area without 

 papulae in center of disk has a radius less than one-third distance from center to 

 edge of paxillar area. 



Superomarginal plates, forty-six in number, from median interradial line to 

 extremity of ray, are nearly vertical in position, the upper ends forming a narrow 

 border to paxillar area. In some specimens the plates slope inward toward the 

 lower end so that the greater part of the plate can be seen from actinal side. Plates 

 are about two-thirds as long as high, very regular, with curved upper end, and are 

 covered with small squamiform spinelets or granules along the median transverse 

 or vertical line, these becoming slenderer and more papilliform toward the edges 

 of the plate, especially in the deep fasciolar grooves, where they are capilliform. 

 At about 1 mm. from upper end of the plate is an erect, slightly flattened, sharp 

 spinule attaining a length of 1 to 1.25 mm., and decreasing in length toward 

 extremity of ray. On first two or three plates they are much reduced in size. 

 Thej^form a regular longituilinal series at border of the abactinal surface, extentling 

 two-thirds to three-fourths length of ray. In typical specimens an occasional 

 plate has a second spinule below the first, and rarely three in a vertical series. 

 Several specimens from station 3308 have twospinules on nearlj* all the plates except 

 in the interradial angle (where the single spinule is not reduced in size) and toward 

 the outer end of series. Similarly, three s})inules occur on a number of infero- 

 marginals, so tliat a side view of ray shows four or five spinules in a vertical series. 



Inferomarginals correspond exactly to superomarginals in number and length, 

 the line separating the two series being straight; plates slope inward, but the exposed 

 surface is strongly arched, forming a rounded margin to actinal surface, the latter 



