ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS— FISHER 155 



half of ray usually no supporting spine. At the end of ray these expanded sheaths 

 are close enough to touch, but become rapidly more and more spaced proximally 

 until they are widely separated over the basal half of ray and oil disk. On the latter 

 region the sheaths surround well developed acioular, cylindrical or even clavate 

 spinules, which may be developed also on the basal parts of the ray especially later- 

 ally. Here, however, they are smaller than on the disk. The form of (lie spines 

 follows the rule for the body generally. 



Abactinal plates small, widely scattered on the ray, and in old specimens becom- 

 ing absorbed. In small and medium-sized specimens a few tongues of overlapping 

 plates extend inward from the supermarginal plates (pi. 79, fig. 1), while on the 

 peripheral parts of disk a disappearing reticulum may be indicated (pi. 79, iig. la). On 

 the central area of disk the subcircular plates are separated, with sometimes ven 

 small discrete platelets scattered in irregular lines and ranks between. These small 

 platelets are similar to, though sometimes more numerous than, the smallest indicated 

 in the above figure. 



Scattered among the papulae, attached often to the hernialike base from which 

 the papulae spring, are numerous very small, long-pedunculate lanceolate straight 

 pedicellariae; or they may form small pedunculate, dermal clusters (pi. 77, figs. 2, 3). 

 There is also a variable number of heavy, ovoid pedunculate pedicellariae, sometimes 

 abundant, reaching a length of 1.75 mm. (PI. 77, fig. 1; pi. 78, figs. 4, 5.) 



The marginal plates, in sharp contrast to the obsolescent abactinal skeleton, are 

 well developed, robust, and form the side wall of the ray. (PI. 79, fig. 1.) They are 

 similar to those of such genera as Orthasterias, and are well hidden by the thick glan- 

 dular skin. Alternate superomarginals have a stout, rather rigid, heavily sheathed 

 spine, upwards of 7 or 8 mm. long in large specimens; and each inferomarginal plate 

 carries two similar, subequal spines sometimes slightly smaller than the supero- 

 marginals. In small specimens each sheath terminates in one to four clusters of 

 crossed pedicellariae, increasing in size with age. (PL 77, figs. 2, 3.) When these 

 are fully developed a complete wreath is formed when the sheath retracts. The 

 form of the spines varies greatly. They may be slender, tapered, with bluntly 

 pointed, or expanded truncate, often compressed, grooved extremities (deep water 

 and some intertidal examples). Numerous intergradations exist between these slen- 

 der spined examples and those with robust spines. Along one sido of a ray the form 

 of a spine may vary greatly. In old specimens the tips become gouge-shaped, or 

 longitudinally grooved or irregularly eroded, sometimes terminating in several points. 

 The first supermarginal spine is spaced distad from the interbrachial angle about 

 one br, while the inferomarginal spines continue toward the actinostome slightly 

 more than one br from tire angle; that is, they begin about midway between mouth 

 plates and the interbrachial angle. 



Adambulacral plates monacanthid, sunken below the actinal face of the infero- 

 m.irginals which form the aetinolateral border of ray. (PI. 77, fig. 3.) The spines 

 are slender, subterete, slightly tapered and blunt. The tip is sometimes compressed. 

 In living or alcoholic specimens the basal part of the spine appears to be rather robust 

 by reason of the integument. On the furrow face of each plate there is usually a 

 pedunculate cluster of small straight pedicellariae of unequal size, or sometimes two 

 clusters. (PI. 77, figs. 1, 3; pi. 78, fig. 5a.) In dried specimens these become occa- 

 sionally plastered to the spinelets which never bear attached pedicellariae. The 

 adoral carina is very long in old specimens and on account of the crowding of the rays 



