ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FI8UER. 365 



The largest sLx-rayed example has five spines in each of the adambulaoral combs, 

 except on out^r part of ray where there are four. The iimcr is sliorler than the 

 out<T three or four, which are subequal, or the outennost a trifle the lonjiest as well 

 as stoutest. The spines are flattened and var>- in thickness in different specimens, 

 being sometimes slightly tapered, sometimes not; tip of first spine bluntly p<)int«d, 

 rough, the rest rough, obtuse, or tnincate. The membrane is thick and (djscures 

 the spines. The edge is emargmate between the spines and fonns usually a rounded 

 tip to each; from the outermost spine the fold extends across the aclinolateral 

 membrane as described by Verrill. Thus the space between each pair of combs 

 is continued as a narrow sulcus toward and even to the margin, as well shown in 

 the photographic figure and in Pcnier's figure of a little specimen. The adam- 

 bulacral structure does not differ in the large seven-rayed example except that 

 proximally there are sLx spines. The outermost is bent away from the rest as 

 described by Verrill in his tyjie from off" Newfoundland Bank. The tip of the spines, 

 as in typical examples, is armed with minute thornlets and is more or less com- 

 presseil and truncate. The number of adand>ulacral spines is variable in sLx-rayed 

 examples, however, for a medium-sized specimen has seven, others six, some five, 

 and small specimens four. The smaller seven-rayed examples have sLx spines 

 proximally. Aperture short and rather broad with a ver^- convex aboral border. 



Mouth spines of the two plates united by a thick continuous web forming a 

 spade-shaped group, five or sLx to a plate and decreasing veiy rapidly from the 

 inner to the outer; the larger spines, especially the innermost, considerably flattened ; 

 the latter longer than interradial diameter of plate. Suboral spine stout, with a 

 hyaline pointed tip, about equal to interradial liiameter of plate, and therefore 

 shorter than innermost oral spine. 



Actinolateral membrane tough, and traversed by continuations of the adam- 

 bulacral fans. The e.xtcnt of the free border is variable. If the supradorsal mem- 

 brane is swollen greatly the fringe is not apparent; otherwise it defines the ambitus, 

 as shown in Perrier's figure. The actinolateral spines are stout, ami hidden by 

 the thick membrane. The tips however are visible, being heavy and truncate. 



Young. — The large seven-rayed example had a young one in the act of escaping 

 through a breach of the supradorsal membrane when killed. This opening is just 

 above the actinolateral border and midway along the side of ray. The membrane 

 was stretched and thin over that point. In one of the smooth interradial regions 

 the membrane was found to l)e thin also, and a cut revealed two young ones beneath, 

 actinal surface uppermost. The larger of these two has U = 10..t mm., r = 7 mm. 

 The one which was escaping has R = 7 mm. Both have six rays, although the parent 

 has seven. The mend)ranes of the young are thin, all the actinal spines being clearly 

 visible. The lateral fringe is prominent. Adambulacral spines five, oral spines 

 five; prominent paxillar spines (as seen from without) four ()r five; spiraeula four 

 or five over each paxilla, cme spiracle between a pair of spines. The general appear- 

 ance of this young one is exactly like tliat of a I'ttraslir with thin mend)ranes. The 

 six rays in the young shows that this is the fundamental nutnlx-r for the species, 

 despite the seven of the parent. 



The slits obsers'ed by Verrill ari' temjxirary only, and may occur elsewhen» 

 than in the interradial regions. They are probably formed periodically in other 



