ASTEEOIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 33 



giving some spocimons a much more robust appearance. The fact that in some 

 examples the abactinal wall is nearly plane, except for the epiproctal cone, and much 

 inflated in others is due, of course, to the condition of the animal at the moment of 

 death, but is important as magnifying one or two trivial characters, such as the angle 

 of marginal plates and compac-tness of paxillie. Two extremes, both from station 

 4223, will serve to illustrate variability of paxillise. Each specimen has K = 34 mm.; 

 in A, paxillffi in neighborhood of madieporic body have seven to twelve spinelets, occa- 

 sionally as few as four on very small ones; of these never more than one is situated 

 in center of tabulum and rather more than half the paxilUc have no central spinelel 

 at all; in B the paxillte ordinarily have from twelve to twenty-two spinelets, of which 

 tliree to five occupy center of tabulum, and all or very nearly all have central spine- 

 lets, those paxillse on outer part of ray having so few as one central spinelet." When 

 these two specimens are placed side by side the difference is very striking. Many 

 of the specimens, both small and large, lack a central spinelet to paxillse altogether, 

 thus resembling exactly some Atlantic examples. There is as much if not more 

 difference in the extremes of these specimens than is shown by Sladen's two figures 

 illustratmg paxUlic of Ctenodiscus australis and C. procurator,'' while in the extremes 

 of body-form the difference is greater than between figures 1 and 7, illustrating the 

 same two species. I thought at first that the difference in size of niadreporic body 

 might furnish a character of some constancy, to separate hrau^ei from crispatus, the 

 latter having the larger body. This character also is very variable in Pacific speci- 

 mens, some examples having fairly large, others small niadreporic bodies. In four 

 rather poorly preserved Atlantic specimens the madreporie body is more constant 

 and is one and one-half times greater in diameter than in Pacific examples of the 

 same size. 



The shaft of the paxilla varies in length. In specimens from very deep water 

 it is longer than in shallow water specimens. 



The bases of paxillre, or the abactinal "plates," are circular and rather closely 

 placed, usually not quite touching. They are largest about one-half r from center 

 of disk, decreasing in size toward tip of ray and center of disk. .Uong mid-radial 

 line where there are no papuhe the plates are smaller antl usuallj^ broadly elliptical. 

 Papulae are not regularly arranged, four to six usually occurring about a plate. 

 They are single, and are lacking on a circular area in center of disk (including the 

 central cone) and on five narrow radial and five narrow interratlial areas extending 

 from the center like the spokes of a wheel. On either side of the radial areas, 

 papulae extend to tip of ray. 



Marginal plates. — Superomarginal plates exactly opposite inferomarginals. The 

 former are thin ami confined to side wall of ray. The actinolateral border of ray 

 with its series of spines is slightly nearer upper than lower border of inferomarginals. 

 The part of inferomarginal below the actinolateral spme has a rather broad special- 

 ized ridge, which is broader than intervening fasciolar furrow. This furrow is 

 roofed over by a single row of spinelets unmersed in a continuous web, eight or 

 nine of these spinelets occurring between lower edge of plate and actinolateral 



o Atlantic specimens show the same range of variation. 

 b Challenger Asteroidea, pi. 30, figs. 4 and 9. 

 '57444°— Bull. 76—11 3 



