ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHEH. 331 



HBTBROZONIAS ALTBRRATUS (Ftahw). 



PI. 9U, fiRS. I-.?; pi. 112. fiRS. 5, 5n-ft. 



Crossaster allematus Fisher, Proc. Wash. Acad. Sci., vol. 8, Aug. 14, 1906, p. 131. 



Diagnosis. — Rays ten. R = 2.6 to 2.9 r. Breadth of ray at base, \ r. Cieneral 

 form flattened; abactinal surface of disk slightly convex, capable of inflation, but 

 flattened on central part; abactinal surface of rays slightly rounded; margins well 

 rounded; actinal surface nearly flat; interbrachial angles rather acute; abactinal 

 skeleton open reticulate, the ossicles slenderer than in S. papposit.f; papulw large; 

 paxillie small, well spaced; marginal plates of two kinds in a single series; more 

 prominently s|)inous transversely ]ilaced paxilliform jjlates alternating with usually 

 two longitudinally oriented plates with very short spinelets; marginal plates actinal 

 in position on basal half of ray; actinal interradial areas small, with few plates set 

 fairly close together; a singh* series of very small intennediate plates extending to 

 end of ray; adambulacral plates with four to eight furrow spinelets and a transverse 

 series of four actinal spinules. 



Description. — Abactinal integument rather thin but tough and pliable, parch- 

 ment-like, quite opaque, and obscuring the ossicles unless drieil. Skeleton open 

 and forming a network with fairly wide meshes, which are irregular and largest on 

 disk; connecting ossicles slender, often irregular; inclosed within meshes, small 

 free irregular ossicles; these often absent, but usuallj' presiMit on disk and most 

 numerous near its center. Paxilla> with a two to four slender-lobed ba.se and a low 

 stout pedicel surmounted by usually four to six, or far along ray two or three, and 

 on disk' sometimes as many as nine, rough, delicate tapering, pointed, spinelets 

 inclosed in a delicate membranous sac, which fits tightly about each spinule for 

 about half its length, leaving onJy its basal part obscured. In consequence of the 

 open character of skeleton, the paxillse are well spaced, but are very much smaller 

 and more numerous than in S. pappnsits. They are largest and most widely spaced 

 on radial areas midway between center of disk and margin, thence rapidly diminish 

 in size toward extremity of ray and less toward center of disk. The paxillsp are 

 not arranged in very evident series, although along the lateral regions of the rays 

 an arrangement in quincunx is observable, though not .so well marke<l as in S. horealis 

 or paxillatus. A bare sulcus leads from each interradial angle halfway to center of 

 disk. These bare areas are about 1 mm. wide and are paved solidly wnth ossicles, 

 which are the upper edge of the incomplete calcareous interbrachial partition. At 

 the inner end of this bare area, in one interradius, is the madre])oric body sur- 

 rounded by several paxillse; in the other radii several slightly larger paxilla' hold 

 a similar position. Papulie large, partially obscuring the small paxilla;; absent 

 from bare interradial areas; two to seven or eight to each mesh of skeleton on rays 

 and as many as fifteen on disk, or even more where meshes are incomplete. Papulte 

 commonly 3 mm. long, pointed. In the interradii a number of the abactinal plates 

 are actinal in position, because the marginal plates are drawn inward toward the 

 mouth. Thus in the type the distance between marginal plates and interradial 

 angle is 6 to 8 mm. Consequently the dorsal integument with plates and papula> 

 is drawn upon actinal surface. 



